Methods and apparatus to fingerprint an audio signal

ABSTRACT

Methods, apparatus, systems, and articles of manufacture to fingerprint an audio signal. An example apparatus disclosed herein includes an audio segmenter to divide an audio signal into a plurality of audio segments, a bin normalizer to normalize the second audio segment to thereby create a first normalized audio segment, a subfingerprint generator to generate a first subfingerprint from the first normalized audio segment, the first subfingerprint including a first portion corresponding to a location of an energy extremum in the normalized second audio segment, a portion strength evaluator to determine a likelihood of the first portion to change, and a portion replacer to, in response to determining the likelihood does not satisfy a threshold, replace the first portion with a second portion to thereby generate a second subfingerprint.

FIELD OF THE DISCLOSURE

This disclosure relates generally to audio signal processing, and, moreparticularly, to methods and apparatus to fingerprint an audio signal.

BACKGROUND

Audio information (e.g., sounds, speech, music, etc.) can be representedas digital data (e.g., electronic, optical, etc.). Captured audio (e.g.,via a microphone) can be digitized, stored electronically, processed,and/or cataloged. One way of cataloging audio information is bygenerating an audio fingerprint. Audio fingerprints are digitalsummaries of audio information created by sampling a portion of theaudio signal. Audio fingerprints have historically been used to identifyaudio and/or verify audio authenticity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example system in which the teachings of this disclosuremay be implemented.

FIG. 2 is an example implementation of the query fingerprint generatorof FIG. 1.

FIG. 3 is an example implementation of the reference fingerprintgenerator of FIG. 1.

FIG. 4A depicts an example unprocessed spectrogram generated by theexample signal transformer of FIG. 2.

FIG. 4B depicts an example of a normalized spectrogram generated by thesignal normalizer of FIG. 2 from the unprocessed spectrogram of FIG. 4A.

FIG. 5A is the content of an audio signal including commercials that canbe processed by the system of FIG. 1.

FIG. 5B is the content of an audio signal including multiple channelchanges that can be processed by the system of FIG. 1.

FIG. 6 is an illustration showing the generation of alternativereference fingerprints output by the reference fingerprint generator ofFIGS. 1 and 3.

FIG. 7 is a flowchart representative of machine-readable instructionsthat may be executed to implement the query fingerprint generator ofFIGS. 1 and 2.

FIG. 8 is a flowchart representative of machine-readable instructionsthat may be executed to implement the reference fingerprint generator ofFIGS. 1 and 3.

FIG. 9 is a block diagram of an example processing platform structuredto execute the instructions of FIG. 7 to implement the referencefingerprint generator of FIGS. 1 and/or 3.

FIG. 10 is a block diagram of an example processing platform structuredto execute the instructions of FIG. 8 to implement the query fingerprintgenerator of FIGS. 1 and/or 3.

The figures are not to scale. Instead, the thickness of the layers orregions may be enlarged in the drawings. In general, the same referencenumbers will be used throughout the drawing(s) and accompanying writtendescription to refer to the same or like parts.

Unless specifically stated otherwise, descriptors such as “first,”“second,” “third,” etc. are used herein without imputing or otherwiseindicating any meaning of priority, physical order, arrangement in alist, and/or ordering in any way, but are merely used as labels and/orarbitrary names to distinguish elements for ease of understanding thedisclosed examples. In some examples, the descriptor “first” may be usedto refer to an element in the detailed description, while the sameelement may be referred to in a claim with a different descriptor suchas “second” or “third.” In such instances, it should be understood thatsuch descriptors are used merely for identifying those elementsdistinctly that might, for example, otherwise share a same name.

DETAILED DESCRIPTION

Fingerprint or signature-based media monitoring techniques generallyutilize one or more inherent characteristics of the monitored mediaduring a monitoring time interval to generate a substantially uniqueproxy for the media. Such a proxy is referred to as a signature orfingerprint, and can take any form (e.g., a series of digital values, awaveform, etc.) representative of any aspect(s) of the media signal(s)(e.g., the audio and/or video signals forming the media presentationbeing monitored). A signature can be a series of sub-signaturescollected in series over a time interval. The term “fingerprint” and“signature” are used interchangeably herein and are defined herein tomean a proxy for identifying media that is generated from one or moreinherent characteristics of the media.

Signature-based media monitoring generally involves determining (e.g.,generating and/or collecting) signature(s) representative of a mediasignal (e.g., an audio signal and/or a video signal) output by amonitored media device and comparing the monitored media signature(s) toone or more reference signatures corresponding to known (e.g.,reference) media sources. Various comparison criteria, such as across-correlation value, a Hamming distance, etc., can be evaluated todetermine whether a monitored signature matches a particular referencesignature.

When a match between the monitored signature and one of the referencesignatures is found, the monitored media can be identified ascorresponding to the particular reference media represented by thereference signature that matched with the monitored media signature.Because attributes, such as an identifier of the media, a presentationtime, a broadcast channel, etc., are collected for the referencesignature, these attributes can then be associated with the monitoredmedia whose monitored signature matched the reference signature. Examplesystems for identifying media based on codes and/or signatures are longknown and were first disclosed in Thomas, U.S. Pat. No. 5,481,294, whichis hereby incorporated by reference in its entirety.

Historically, audio fingerprinting technology has used the loudest parts(e.g., the parts with the most energy, etc.) of an audio signal tocreate fingerprints in a time segment. In some examples, the loudestparts of an audio signal can be associated with noise (e.g., unwantedaudio) and not from the audio of interest. In some examples,fingerprints generated using historic audio fingerprint technology wouldbe generated based on the background noise and not of the audio ofinterest, which reduces the usefulness of the generated fingerprint.Additionally, fingerprints of music generated using these historic audiofingerprint technologies often are not generated information from allparts of the audio spectrum that can be used for signature matchingbecause the bass spectrum of audio tends to be louder than otherfrequencies spectra in the audio (e.g., treble ranges, etc.). Someexample methods, apparatus, systems, and articles of manufacture toovercome the above-noted deficiencies by generating fingerprints usingmean normalization and are disclosed in U.S. patent application Ser. No.16/453,654, which is hereby incorporated by reference in its entirety.

Audio signaturing technologies, like the technologie(s) disclosed inU.S. patent application Ser. No. 16/453,654, use characteristics oftemporal adjacent audio spectra characteristics to normalize specificaspects of the audio signal. The normalized audio spectra are then usedto generate audio fingerprints. That is, the fingerprint of a specificportion of an audio signal is based upon a temporal window of the audiosignal around that specific portion (e.g., a six second audio window,etc.). This non-local dependence can cause adverse effects on queryfingerprint generation and reference fingerprint generation due toboundary/edge effects. For example, if the audio signal includesmultiple audio sources (e.g., multiple commercials during an audiosignal associated with a commercial break, an audio signal including asong transition, an audio signal including a channel change, etc.), thefingerprint of one audio source may generated based partially on theaudio characteristics of the adjacent sources.

Method and apparatus disclosed herein overcome the abovenoted-deficiencies by determining the relative strength of the portionsof the subfingerprints of a fingerprint. In some examples disclosedherein, each portion of a subfingerprint can be characterized based onhow dependent the value of that portion is on the variations in thesurrounding audio signal region. In such examples disclosed herein, weakportions of a subfingerprint correspond to portions of a subfingerprintthat frequently change due to noise or surrounding characteristics ofthe audio signal. In such examples disclosed herein, strong portions ofa subfingerprint correspond to portions of a subfingerprint thatinfrequently change due to noise or surrounding characteristics of theaudio signal. In some examples disclosed herein, during referencefingerprint generation, alternative fingerprints can be generated basedon the identified weak subfingerprint portions based on the probabilityof their occurrences. In some examples disclosed herein, during thegeneration of a query fingerprint, modified query fingerprints can begenerated by changing the weak portions of the query fingerprint. Insome examples disclosed herein, weak portions of the subfingerprint canbe excluded during fingerprint matching.

FIG. 1 is an example system 100 in which the teachings of thisdisclosure can be implemented. The example system 100 includes anexample audio source 102, an example microphone 104 that captures soundfrom the audio source 102 and converts the captured sound into anexample audio signal 106. An example query fingerprint generator 108receives the audio signal 106 and generates one or more example queryfingerprint(s) 110, which is transmitted over an example network 111 toan example central facility 112. The central facility 112 includes anexample fingerprint comparator 114, which matches the example queryfingerprint(s) 110 to fingerprints of an example reference fingerprintdatabase 116 to generate an example media identification report 115. Theexample reference fingerprint database 116 includes referencefingerprints generated by a reference fingerprint generator 120. In theillustrated example of FIG. 1, the reference fingerprint generator 120generates reference fingerprints based on a reference audio signal 118.

The example audio source 102 emits an audible sound. The example audiosource can be a speaker (e.g., an electroacoustic transducer, etc.), alive performance, a conversation, and/or any other suitable source ofaudio. The example audio source 102 can include desired audio (e.g., theaudio to be fingerprinted, etc.) and can also include undesired audio(e.g., background noise, etc.). In the illustrated example, the audiosource 102 is a speaker. In other examples, the audio source 102 can beany other suitable audio source (e.g., a person, etc.).

The example microphone 104 is a transducer that converts the soundemitted by the audio source 102 into the audio signal 106. In someexamples, the microphone 104 can be a component of a computer, a mobiledevice (a smartphone, a tablet, etc.), a navigation device, or awearable device (e.g., a smartwatch, etc.). In some examples, themicrophone can include an analog-to digital converter to digitize theaudio signal 106. In other examples, the query fingerprint generator 108can digitize the audio signal 106.

The example audio signal 106 is a digitized representation of the soundemitted by the audio source 102. In some examples, the audio signal 106can be saved on a computer before being processed by the queryfingerprint generator 108. In some examples, the audio signal 106 can betransferred over a network (e.g., the network 111, etc.) to the examplequery fingerprint generator 108. Additionally or alternatively, anyother suitable method can be used to generate the audio (e.g., digitalsynthesis, etc.).

The example query fingerprint generator 108 converts the example audiosignal 106 into the example query fingerprint(s) 110. In some examples,the query fingerprint generator 108 can convert some or all of the audiosignal 106 into the frequency domain. In some examples, the queryfingerprint generator 108 divides the audio signal into time-frequencybins. In some examples, the audio characteristic is the energy of theaudio signal. In other examples, any other suitable audio characteristiccan be determined and used to normalize each time-frequency bin (e.g.,the entropy of the audio signal, etc.). In some examples, the queryfingerprint generator 108 identifies the weak portions of the queryfingerprint(s) 110 and modifies the query fingerprint(s) 110 to replacethe identified weak portions. Additionally or alternatively, anysuitable means can be used to generate the query fingerprint(s) 110. Insome examples, some or all of the components of the query fingerprintgenerator 108 can be implemented by a mobile device (e.g., a mobiledevice associated with the microphone 104, etc.). In other examples, thequery fingerprint generator 108 can be implemented by any other suitabledevice(s). An example implementation of the query fingerprint generator108 is described below in conjunction with FIG. 2.

The example query fingerprint(s) 110 are a condensed digital summary ofthe audio signal 106 that can be used to identify and/or verify theaudio signal 106. For example, the query fingerprint(s) 110 can begenerated by sampling portions of the audio signal 106 and processingthose portions. In some examples, the query fingerprint(s) 110 iscomposed of a plurality of subfingerprints, which correspond to distinctsamples of the audio signal 106. In some examples, the queryfingerprint(s) 110 is associated with a period of time (e.g., sixseconds, 48 seconds, etc.) of audio signal 106. In some examples, thequery fingerprint(s) 110 can include samples of the highest energyportions of the audio signal 106. In some examples, the queryfingerprint(s) 110 can be used to identify the audio signal 106 (e.g.,determine what song is being played, etc.). In some examples, the queryfingerprint(s) 110 can be used to verify the authenticity of the audiosignal 106.

The example network 111 is a network that allows the queryfingerprint(s) 110 to be transmitted to the central facility 112 andfingerprint comparator 114. For example, the network 111 is a local areanetwork (LAN), a wide area network (WAN), etc. In some examples, thenetwork 111 is the Internet. In some examples, the network 111 is awired connection. In some examples, the network 111 is absent. In suchexamples, the query fingerprint(s) 110 can be transmitted to the centralfacility 112 by any other suitable means (e.g., a physical storagedevice, etc.). Additionally or alternatively, the query fingerprintgenerator 108, the reference fingerprint generator 120, and/or thefingerprint comparator 114 can be implemented by or at the same device(e.g., a server at the central facility 112 of media monitoring entity,etc.).

The central facility 112 is a facility operated to analyze referencefingerprints, associated with an interested party to analyze, identify,and categorize audio signals (e.g., a media monitoring entity, a mediaprovider, etc.). In some examples, the central facility 112 can beinclude and/or be implemented by a server. In some examples, the centralfacility 112 can be implemented by a cloud service, a distributed systemat several locations, and/or any other suitable means. In theillustrated example of FIG. 1, the central facility 112 includes thefingerprint comparator 114, the reference fingerprint database 116, andthe reference fingerprint generator 120. In other examples, thefingerprint comparator 114, the reference fingerprint database 116, andthe reference fingerprint generator 120 can be implemented at any othersuitable location (e.g., at a user device, at a third party location,etc.).

The example fingerprint comparator 114 receives and processes the queryfingerprint(s) 110. For example, the fingerprint comparator 114 canmatch the query fingerprint(s) 110 to one or more referencefingerprint(s) stored in the reference fingerprint database 116. In someexamples, the fingerprint comparator 114 can determine the queryfingerprint(s) 110 matches none of the reference fingerprints stored inthe reference fingerprint database 116. In such examples, thefingerprint comparator 114 returns a result indicating the mediaassociated with the reference fingerprint could not be identified. Insome examples, one of the query fingerprint(s) 110 can be compared tomultiple reference fingerprints associated with one reference audiosignal. In such examples, a match with any of the reference fingerprintsindicates the query fingerprint(s) 110 is associated with the same mediaas the reference audio signal 118. Additionally or alternatively,multiple query fingerprint(s) 110 can be compared with the referencefingerprint(s) 121. In some such examples, a match with any of thereference fingerprints indicates the query fingerprint(s) 110 isassociated with the same media as the reference audio signal 118.

The reference fingerprint database 116 stores a plurality of referencefingerprint(s) corresponding to one or more pre-identified pieces ofmedia. The reference fingerprint database 116 can be implemented by avolatile memory (e.g., a Synchronous Dynamic Random Access Memory(SDRAM), Dynamic Random Access Memory (DRAM), RAMBUS Dynamic RandomAccess Memory (RDRAM), etc.) and/or a non-volatile memory (e.g., flashmemory). The reference fingerprint database 116 can additionally oralternatively be implemented by one or more double data rate (DDR)memories, such as DDR, DDR2, DDR3, DDR4, mobile DDR (mDDR), etc. Thereference fingerprint database 116 can additionally or alternatively beimplemented by one or more mass storage devices such as hard diskdrive(s), compact disk drive(s), digital versatile disk drive(s),solid-state disk drive(s), etc. In the illustrated example of FIG. 1,the reference fingerprint database 116 is illustrated as a singledatabase. In other examples, the reference fingerprint database 116 canbe implemented by any number and/or type(s) of databases. Furthermore,the reference fingerprint(s) stored in the reference fingerprintdatabase 116 may be in any data format. (e.g., an 8 bit integer number,a 32 bit floating point number, etc.).

The reference audio signal 118 is a digitized representation of thesound emitted. In some examples, the reference audio signal 118 is audiocaptured by a microphone in a manner similar to the audio signal 106. Inother examples, the reference audio signal can be already digitizedaudio received (e.g., extracted, etc.) from a storage medium (e.g., ahard disk, a compact disk (CD), a record, a cassette, etc.) and/oranother type of media (e.g., the audio of a movie, the audio oftelevision program, the audio of streaming media, etc.). In someexamples, the reference audio signal 118 is provided to the centralfacility 112 by an interested party (e.g., a publisher of the audio,etc.). In such examples, the reference audio signal 118 can betransferred over a network to the reference fingerprint generator 120.

The reference fingerprint generator 120 converts the example referenceaudio signal 118 into the example reference fingerprint 121. Forexample, the reference fingerprint generator 120 can convert thereference audio signal 118 into the reference fingerprint(s) 121 in amanner similar to that of the query fingerprint generator 108. In otherexamples, the reference fingerprint generator 120 can convert thereference audio signature by any other suitable means. An exampleimplementation of the reference fingerprint generator 120 is describedbelow in conjunction with FIG. 3.

The reference fingerprint(s) 121 is/are a condensed digital summary ofthe reference audio signal 118 that can be used to identifies thereference audio signal 118. The reference fingerprint(s) 121 generallyhave the same structure as the query fingerprint(s) 110. For example,the reference fingerprint(s) 121 is composed of a plurality ofsubfingerprints, which correspond to distinct samples of the referenceaudio signal 118. As such, the query fingerprint(s) 110 can be comparedto the reference fingerprint(s) 121. In some examples, the referencefingerprint(s) 121 can be formatted differently than the queryfingerprint(s) 110. For example, the reference fingerprint(s) 121 can begenerated at a higher fidelity and/or at a different sample rate thanthe query fingerprint(s) 110.

FIG. 2 is an example implementation of the example query fingerprintgenerator 108 of FIG. 1. The example query fingerprint generator 108includes an example audio signal interface 202, an example audiosegmenter 204, an example signal transformer 206, an example audiocharacteristic determiner 208, an example bin normalizer 210, an examplesubfingerprint generator 212, an example portion strength evaluator 214,an example portion replacer 216, and an example fingerprint generator218.

The example audio signal interface 202 receives the digitized audiosignal from the microphone 104. In some examples, the audio signalinterface 202 can request the digitized audio signal from the microphone104 periodically. In other examples, the audio signal interface 202 canreceive the audio signal 106 from the microphone 104 as soon as theaudio is detected. In some examples when the microphone 104 is absent,the audio signal interface 202 can request the digitized audio signal106 from a database. In some examples, the audio signal interface 202can include an analog-to-digital converter to convert the audio receivedby the microphone 104 into the audio signal 106.

The example audio segmenter 204 divides the audio signal 106 into audiosegments (e.g., frames, periods, etc.). For example, the audio segmentercan divide the audio signal 106 into discrete audio segmentscorresponding to unique portions of the audio signal 106. In someexamples, the audio segmenter 204 determines which portions of the audiosignal 106 correspond to each of the generated audio segments. In someexamples, the audio segmenter 204 can generate segments of any suitablesize.

The example signal transformer 206 transforms portions of the audiosignal of the digitized audio signal 106 into the frequency domain. Forexample, the signal transformer 206 performs a fast Fourier transform(FFT) on an audio signal 106 to transform the audio signal 106 into thefrequency domain. In other examples, the signal transformer 206 can useany suitable technique to transform the audio signal 106 (e.g., discreteFourier transforms, a sliding time window Fourier transform, a wavelettransform, a discrete Hadamard transform, a discrete Walsh Hadamard, adiscrete cosine transform, etc.). In some examples, each time-frequencybin has an associated magnitude (e.g., the magnitude of the transformedsignal in that time-frequency bin, etc.). In some examples, the signaltransformer 206 can be implemented by one or more band-pass filters(BPFs). In some examples, the output of the example signal transformer206 can be represented by a spectrogram. In some examples, the signaltransformer 206 works concurrently with the audio segmenter 204. Anexample output of the signal transformer 206 is discussed below inconjunction with FIG. 4A.

The example audio characteristic determiner 208 determines the audiocharacteristic(s) of a portion of the audio signal 106 (e.g., an audioregion associated with a time-frequency bin, etc.). The audiocharacteristic determiner 208 can determine the audio characteristics ofa group of time-frequency bins (e.g., the energy of the portion of theaudio signal 106 corresponding to each time-frequency bin in a group oftime-frequency bins, the entropy of the portion of the audio signal 106corresponding to each time-frequency bin in a group of time-frequencybins, etc.). For example, the audio characteristic determiner 208 candetermine the mean energy (e.g., average power, etc.) of one or more ofthe audio regions associated with an audio region (e.g., the mean of themagnitudes squared of the transformed signal corresponding to thetime-frequency bins in the region, etc.) adjacent to a selectedtime-frequency bin. In other examples, the audio characteristicdeterminer 208 can determine the mean entropy of one or more of theaudio regions associated with an audio region (e.g., the mean of themagnitudes of the time-frequency bins in the region, etc.) adjacent to aselected time-frequency bin. In other examples, the audio characteristicdeterminer 208 can determine the mean energy and/or mean entropy by anyother suitable means. Additionally or alternatively, the audiocharacteristic determiner 208 can determine other characteristics of aportion of the audio signal (e.g., the mode energy, the median energy,the mode power, the median energy, the mean energy, the mean amplitude,etc.).

The example bin normalizer 210 normalizes one or more time-frequencybins by an associated audio characteristic of the surrounding audioregion. For example, the bin normalizer 210 can normalize atime-frequency bin by a mean energy of the surrounding audio region. Inother examples, the bin normalizer 210 normalizes some of the audiosignal frequency bins by an associated audio characteristic of thesurrounding audio region. For example, the bin normalizer 210 cannormalize each time-frequency bin using the mean energy associated withthe audio region surrounding that time-frequency bin. In some examples,the output of the bin normalizer 210 (e.g., a normalized time-frequencybin, etc.) can be represented as a spectrogram.

The example subfingerprint generator 212 generates subfingerprintsassociated with an audio sample(s) and/or audio segment at a samplerate. In some examples, the subfingerprint generator 212 generates asubfingerprint of a sample after the bin normalizer 214 has normalizedthe energy value of each time-frequency bin in an audio segment. In someexamples, the subfingerprint generator 212 generates the subfingerprintassociated with a sample based on the energy extrema of the normalizedtime-frequency bins within the sample. In some examples, thesubfingerprint generator 212 selects a group of time-frequency bins(e.g., one bin, five bins, 20 bins, etc.) with the highest normalizedenergy values in a sample to generate a subfingerprint. In suchexamples, each portion of the subfingerprints generated bysubfingerprint generator 212 is associated with a location of aparticular energy extremum in the normalized spectrogram generated bythe bin normalizer 210.

The example portion strength evaluator 214 evaluates the strength ofeach portion of the subfingerprints generated by the subfingerprintgenerator 212. For example, the portion strength evaluator 214 canrepeat the subfingerprint generation process (e.g., the process executedby the example signal transformer 206, the example audio characteristicdeterminer 208, the example bin normalizer 210, the examplesubfingerprint generator 212, etc.) but overlaying the audio signal withrandomly generated noise (e.g., white noise, artificially generatedbackground audio, etc.). In some examples, because the subfingerprintsassociated with each audio sample depend on audio characteristics ofadjacent samples, the portion strength evaluator 214 can determine thestrength of the portions of a subfingerprint by changing the audiocharacteristics of adjacent audio samples. For example, forsubfingerprints associated with temporal ends of the audio signal 106(e.g., the beginning of the audio signal, the end of the audio signal),the portion strength evaluator 214 can append different audio (e.g.,white noise, artificially generated background audio, other media,etc.). Additionally or alternatively, the portion strength evaluator 214can, for some or all samples of the audio signal, replace the adjacentaudio samples with different audio (e.g., white noise, artificiallygenerated background audio, different media, etc.).

Based on how the portions of subfingerprints change, the portionstrength evaluator 214 can label portions of a subfingerprint as “weak,”“strong,” or “neutral.” As used herein, a weak portion of asubfingerprint frequently changes based on audio overlays or adjacentfeature testing. As used herein, a strong portion of a subfingerprintdoes not frequently change based on audio overlays or adjacent featuretesting. As used herein, a neutral portion of a subfingerprint isportion of the subfingerprint that is neither strong nor weak portions.In some examples, the portion strength evaluator 214 determines thestrength of a portion of subfingerprint based on one or more strengththreshold. In such examples, the portion strength evaluator 214 canconduct a plurality of trials (e.g., multiple noise overlays, multiplesample replacements, etc.) and count the number of times a given portionof subfingerprint changes. In some examples, if a portion changes morethan a weak strength threshold is identified as a weak portion. In someexamples, if a portion changes less than a strong strength threshold,the portion is identified as a strong portion. In some examples, if aportion satisfies neither the weak nor strong thresholds, the portion isidentified as a neutral.

The example portion replacer 216 replaces portions of the generatedsubfingerprint generator 212 identified as weak by the portion strengthevaluator 214. For example, the portion replacer 216 can replace weakportions of generated subfingerprints with random audio. In suchexamples, the portion replacer 216 can replace some or all of theidentified weak portions with a random portion. For example, the portionreplacer 216 can replace the weak portions with audio generated duringthe operation of the portion strength evaluator 214. In other examples,the portion replacer 216 can replace the identified weak portions withany other suitable portion.

The example fingerprint generator 218 generates a fingerprint based onthe subfingerprints generated by the subfingerprint generator 212 and/orthe portion replacer 216. For example, the fingerprint generator 218 cangenerate the query fingerprint(s) 110 based on the subfingerprints(e.g., query subfingerprints, etc.) generated by the subfingerprintgenerator 212. For example, the fingerprint generator 218 canconcatenate the subfingerprints associated with each audio segment intothe query fingerprint(s) 110. In some examples, the fingerprintgenerator 218 can generate a fingerprint including the subfingerprintsin which the weak portions have been replaced by the portion replacer216. In some examples, the fingerprint generator 218 can generatemultiple query fingerprints based on the portions of thesubfingerprints. In such examples, the fingerprint generator 218 cangenerate fingerprints including different subfingerprints of which theweak portions have been replaced. In some examples, the portion replacer216 can be omitted. In such examples, the fingerprint generator 218 cangenerate multiple fingerprints based on different audio overlays and/oraudio sample appendages.

While an example manner of implementing the query fingerprint generator108 of FIG. 1 is illustrated in FIG. 2, one or more of the elements,processes and/or devices illustrated in FIG. 2 may be combined, divided,re-arranged, omitted, eliminated and/or implemented in any other way.Further, the example audio signal interface 202, the example audiosegmenter 204, the example signal transformer 206, the example audiocharacteristic determiner 208, the example bin normalizer 210, theexample subfingerprint generator 212, the example portion strengthevaluator 214, the example portion replacer 216, an example fingerprintgenerator 218, and/or, more generally, the example query fingerprintgenerator 108 of FIG. 2 may be implemented by hardware, software,firmware and/or any combination of hardware, software and/or firmware.Thus, for example, any of the example audio signal interface 202, theexample audio segmenter 204, the example signal transformer 206, theexample audio characteristic determiner 208, the example bin normalizer210, the example subfingerprint generator 212, the example portionstrength evaluator 214, the example portion replacer 216, an examplefingerprint generator 218, and/or, more generally, the example queryfingerprint generator 108 could be implemented by one or more analog ordigital circuit(s), logic circuits, programmable processor(s),programmable controller(s), graphics processing unit(s) (GPU(s)),digital signal processor(s) (DSP(s)), application specific integratedcircuit(s) (ASIC(s)), programmable logic device(s) (PLD(s)) and/or fieldprogrammable logic device(s) (FPLD(s)). When reading any of theapparatus or system claims of this patent to cover a purely softwareand/or firmware implementation, at least one of the example audio signalinterface 202, the example audio segmenter 204, the example signaltransformer 206, the example audio characteristic determiner 208, theexample bin normalizer 210, the example subfingerprint generator 212,the example portion strength evaluator 214, the example portion replacer216, an example fingerprint generator 218, is/are hereby expresslydefined to include a non-transitory computer readable storage device orstorage disk such as a memory, a digital versatile disk (DVD), a compactdisk (CD), a Blu-ray disk, etc. including the software and/or firmware.Further still, the example query fingerprint generator 108 of FIG. 2 mayinclude one or more elements, processes and/or devices in addition to,or instead of, those illustrated in FIG. 2, and/or may include more thanone of any or all of the illustrated elements, processes, and devices.As used herein, the phrase “in communication,” including variationsthereof, encompasses direct communication and/or indirect communicationthrough one or more intermediary components, and does not require directphysical (e.g., wired) communication and/or constant communication, butrather additionally includes selective communication at periodicintervals, scheduled intervals, aperiodic intervals, and/or one-timeevents.

FIG. 3 is an example implementation of the reference fingerprintgenerator 120 of FIG. 1. In the illustrated example of FIG. 3, thereference fingerprint generator 120 includes an example reference audiosignal interface 302 and an example reference fingerprint generator 304.In the illustrated example of FIG. 3, the reference fingerprintgenerator 120 includes the example audio segmenter 204 of FIG. 2, theexample signal transformer 206 of FIG. 2, the example audiocharacteristic determiner 208 of FIG. 2, the example bin normalizer 210of FIG. 2, the example subfingerprint generator 212 of FIG. 2, theexample portion strength evaluator 214, and the portion replacer 216 ofFIG. 2. Unless stated otherwise, the audio segmenter 204 of FIG. 3, thesignal transformer 206 of FIG. 3, the example audio characteristicdeterminer 208 of FIG. 3, the example bin normalizer 210 of FIG. 3, theexample subfingerprint generator 212 of FIG. 3, the example portionstrength evaluator 214, and the portion replacer 216 of FIG. 3 functionsubstantially as the counterparts described in conjunction with FIG. 2unless stated otherwise.

The example reference audio signal interface 302 receives the referenceaudio signal 118. In some examples, the reference audio signal interface302 receives a digitized reference audio signal 118 (e.g., actual audiocaptured by a microphone, transferred over a network, etc.). In someexamples, the reference audio signal interface 302 can be implemented byaudio processing hardware (e.g., a CD-player, a record player, etc.) Insome examples when the microphone 104 is absent, the audio signalinterface 202 can request the reference audio signal 118 from adatabase. In some examples, the audio signal interface 202 can includean analog-to-digital converter to convert the audio into the referenceaudio signal 118.

The example reference fingerprint generator 304 generates a fingerprintbased on the subfingerprints. For example, the reference fingerprintgenerator 304 can generate the reference fingerprint(s) 121 based on thesubfingerprints (e.g., reference subfingerprints, etc.) generated by thesubfingerprint generator 212. For example, the fingerprint generator 218can concatenate the subfingerprints associated with each audio segmentinto the query fingerprint(s) 110. In some examples, the fingerprintgenerator 218 can generate multiple reference fingerprints based on theportions of the subfingerprints. For example, the reference fingerprintgenerator 304 can generate two or more reference fingerprint(s) 121. Insuch examples, the reference fingerprint generator 304 can storemultiple reference fingerprints in the reference fingerprint database116. During matching, a generated query fingerprint (e.g., the queryfingerprint(s) 110 of FIG. 1) can be compared to each of the relatedreference fingerprint(s) 121.

While an example manner of implementing the reference fingerprintgenerator 120 of FIG. 1 is illustrated in FIG. 3, one or more of theelements, processes and/or devices illustrated in FIG. 3 may becombined, divided, re-arranged, omitted, eliminated and/or implementedin any other way. Further, the example reference audio signal interface302, the example audio segmenter 204, the example signal transformer206, the example audio characteristic determiner 208, the example binnormalizer 210, the example subfingerprint generator 212, the exampleportion strength evaluator 214, the example portion replacer 216, theexample reference fingerprint generator 304, and/or, more generally, theexample reference fingerprint generator 120 of FIG. 3 may be implementedby hardware, software, firmware and/or any combination of hardware,software and/or firmware. Thus, for example, any of the examplereference audio signal interface 302, the example audio segmenter 204,the example signal transformer 206, the example audio characteristicdeterminer 208, the example bin normalizer 210, the examplesubfingerprint generator 212, the example portion strength evaluator214, the example portion replacer 216, the example reference fingerprintgenerator 304 and/or, more generally, the example reference fingerprintgenerator 120 could be implemented by one or more analog or digitalcircuit(s), logic circuits, programmable processor(s), programmablecontroller(s), graphics processing unit(s) (GPU(s)), digital signalprocessor(s) (DSP(s)), application specific integrated circuit(s)(ASIC(s)), programmable logic device(s) (PLD(s)) and/or fieldprogrammable logic device(s) (FPLD(s)). When reading any of theapparatus or system claims of this patent to cover a purely softwareand/or firmware implementation, at least one of the example referenceaudio signal interface 302, the example audio segmenter 204, the examplesignal transformer 206, the example audio characteristic determiner 208,the example bin normalizer 210, the example subfingerprint generator212, the example portion strength evaluator 214, the example portionreplacer 216, the example reference fingerprint generator 304, is/arehereby expressly defined to include a non-transitory computer readablestorage device or storage disk such as a memory, a digital versatiledisk (DVD), a compact disk (CD), a Blu-ray disk, etc. including thesoftware and/or firmware. Further still, the example referencefingerprint generator 120 of FIG. 3 may include one or more elements,processes and/or devices in addition to, or instead of, thoseillustrated in FIG. 4, and/or may include more than one of any or all ofthe illustrated elements, processes, and devices. As used herein, thephrase “in communication,” including variations thereof, encompassesdirect communication and/or indirect communication through one or moreintermediary components, and does not require direct physical (e.g.,wired) communication and/or constant communication, but ratheradditionally includes selective communication at periodic intervals,scheduled intervals, aperiodic intervals, and/or one-time events.

FIG. 4A depicts an example unprocessed spectrogram 400 generated by theexample signal transformer 206 of FIG. 2. In the illustrated example ofFIG. 4A, the example unprocessed spectrogram 400 includes an examplefirst time-frequency bin 404 surrounded by an example first audio region406. The example unprocessed spectrogram 400 of FIG. 4A includes anexample vertical axis 408 denoting frequency bins and an examplehorizontal axis 410 denoting time bins. In the illustrated example ofFIG. 4A, the spectrogram 400 is divided into example first edge region412A, an example second edge region 412B, and a center region 414. Theexample unprocessed spectrogram 400 further includes an example secondtime-frequency bin 418 surrounded by an example second audio region 420.

The example first audio region 406 from which the normalization audiocharacteristic is derived by the audio characteristic determiner 208 andused by the bin normalizer 210 to normalize the first time-frequencybins 404. In the illustrated example, each time-frequency bin of theunprocessed spectrogram 400 is normalized to generate a normalizedspectrogram. In other examples, any suitable number of thetime-frequency bins of the unprocessed spectrogram 400 can be normalizedto generate a normalized spectrogram. An example normalized spectrogramgenerated by the bin normalizer 210 of FIGS. 2 and 3 is depicted in FIG.4C.

The example vertical axis 408 has frequency bin units generated by afast Fourier Transform (FFT) and has a length of 1024 FFT bins. In otherexamples, the example vertical axis 308 can be measured by any othersuitable techniques of measuring frequency (e.g., Hertz, anothertransformation algorithm, etc.). In some examples, the vertical axis 408encompasses the entire frequency range of the audio signal 106 and/orreference audio signal 118. In other examples, the vertical axis 408 canencompass a portion of the audio signal 106 and/or the reference audiosignal 118.

In the illustrated examples, the example horizontal axis 410 representsa time period of the unprocessed spectrogram 400 that has a total lengthof 11.5 seconds. In the illustrated example, horizontal axis 410 hassixty-four milliseconds (ms) intervals as units. In other examples, thehorizontal axis 410 can be measured in any other suitable units (e.g., 1second, etc.). For example, the horizontal axis 410 encompasses thecomplete duration of the audio. In other examples, the horizontal axis410 can encompass a portion of the duration of the audio signal 106. Inthe illustrated example, each time-frequency bin of the spectrograms300, 302 has a size of 64 ms by 1 FFT bin.

In the illustrated example of FIG. 4A, the first time-frequency bin 404is associated with an intersection of a frequency bin and a time bin ofthe unprocessed spectrogram 400 and a portion of the audio signal 106 orreference audio signal 118 associated with the intersection. The examplefirst audio region 406 includes the time-frequency bins within apre-defined distance away from the example first time-frequency bin 404.For example, the audio characteristic determiner 208 can determine thevertical length of the first audio region 406 (e.g., the length of theaudio region 306A along the vertical axis 408, etc.) based on a setnumber of FFT bins (e.g., 5 bins, 11 bins, etc.). Similarly, the audiocharacteristic determiner 208 can determine the horizontal length of thefirst audio region 406 (e.g., the length of the first audio region 406along the horizontal axis 410, etc.). In the illustrated example, thefirst audio region 406 is a square. Alternatively, the first audioregion 406 can be any suitable size and shape and can contain anysuitable combination of time-frequency bins (e.g., any suitable group oftime-frequency bins, etc.) within the unprocessed spectrogram 400. Theexample audio characteristic determiner 208 can then determine an audiocharacteristic of time-frequency bins contained within the first audioregion 406 (e.g., mean energy, etc.). Using the determined audiocharacteristic, the bin normalizer 210 of FIGS. 2 and/or 3 can normalizean associated value of the first time-frequency bin 404 (e.g., theenergy of first time-frequency bin 404 can be normalized by the meanenergy of each time-frequency bin within the first audio region 406).

FIG. 4B depicts an example of a normalized spectrogram 416 generated bythe bin normalizer 210 of FIGS. 2 and/or 3 from the unprocessedspectrogram 400 of FIG. 4A by normalizing a plurality of thetime-frequency bins of the unprocessed spectrogram 400 of FIG. 4A. Thenormalized spectrogram 416 includes the vertical axis 408 of FIG. 4Adenoting frequency bins and the horizontal axis 410 of FIG. 4A denotingtime bins. The spectrogram 416 is divided into the edge regions 412A,412B, and the center region 414.

For example, some or all of the time-frequency bins of the unprocessedspectrogram 400 can be normalized in a manner similar to how the firsttime-frequency bin 404A was normalized. The normalization of the audiosignal 106 and subsequent generation of the query fingerprint(s) 110 isdescribed below in conjunction with FIG. 7. The normalization andsubsequent generation of the reference fingerprint(s) 121 of thereference audio signal 118 is described below in conjunction with FIG.8. The resulting frequency bins depicted FIG. 4B have now beennormalized by the local mean energy within the local area around theregion. As a result, the darker regions are areas that have the mostenergy in their respective local area. This allows the fingerprint toincorporate relevant audio features even in areas that are low in energyrelative to the usual louder bass frequency area.

The spectrograms 400, 416 of FIGS. 4A-4B are divided into the exampleedge regions 412A, 412B, and the example center region 414. The exampleedge regions 412A, 412B are the portions of the spectrograms 400, 416that the audio regions (e.g., the second audio region 420 of FIG. 4A,etc.) associated with the time-frequency bins (e.g., the secondtime-frequency bin 418 of FIG. 4A, etc.) extends outside the edges ofthe spectrograms 400, 416. If the audio signal 106 is a discrete signal(e.g., the temporal entirety of the audio signal 106 is represented inthe spectrogram 400, etc.), the audio characteristic determiner 208 andbin normalizer 210 can ignore the portion of the audio region 420without defined characteristics (e.g., there is no portion of thespectrogram associated with that portion of the region, etc.). In otherexamples, if the audio signal 106 is discrete, the audio characteristicdeterminer 208 and bin normalizer 210 can account for the undefinedregion by any other suitable method. If the audio signal 106 is not adiscrete signal (e.g., is part of a continuous stream of audio, etc.),the audio characteristic determiner 208 may be capturing audio signalcharacteristics not associated with the audio signal 106. For example,if the audio signal 106 is a portion of an audio stream associated witha commercial, when the bin normalizer 210 normalizes the time-frequencybins in the first edge region 412A (e.g., the audio from the beginningof the commercial, etc.), each of those time-frequency bins isnormalized by a value partially based on the audio characteristics ofthe audio immediately proceeding media (e.g., the television program,the radio program, a different commercial, etc.). Accordingly, thevalues of the time-frequency bins in the edge regions 412A, 412B of thenormalized spectrogram 416 can vary based on the adjacent audio despitethe audio signal 106 being the same. This variance in the normalizedspectrogram 416 results in variance in audio fingerprints generatedtherefrom, which decreases the likelihood of a positive match withreference fingerprints identifying the media associated with the audiosignal 106.

FIG. 5A is the content of an example media stream 500 including examplemedia 502, an example first commercial 504, an example second commercial506, and example third commercial 508 that can be processed by thesystem 100 of FIG. 1. The example commercials 504, 506, 508 have beenprocessed by the query fingerprint generator 108 of FIGS. 1 and/or 2 togenerate corresponding an example first query fingerprint 505, anexample second query fingerprint 507, and an example third queryfingerprint 509, respectively. The example commercials also have anexample reference fingerprint 510, an example second referencefingerprint 512, and an example third reference fingerprint 514,respectively, stored in the reference fingerprint database 116. Theexample media stream includes an example first content change point 518Abetween the media 502 (e.g., media airing in a television broadcast,etc.) and the first commercial 504, an example second content changepoint 518B between the first commercial 504 and the second commercial506, a third content change point 518C, and an example fourth contentchange point 518D.

The media stream 500 is a stream of audio and/or video content thatincludes audio. The media stream 500 can be associated with a radiobroadcast, a television broadcast, streaming media, and/or any othertype of media presentation. The media stream 500 includes differentmedia content arranged continuously. In the illustrated example of FIG.5A, the media stream 500 includes the example media 502 and the examplecommercials 504, 506, 508. In other examples, the media stream 500 caninclude different commercials and/or repeated instances of the samecommercial (e.g., multiple instances of the first commercial 504, etc.).The media 502 can include any suitable content associated with the mediastream (e.g., music, television programming, etc.).

The commercials 504, 506, 508 are relatively short pieces of media usedto advertise various products, services, and/or other things ofpotential issues to consumers of the media 502. The commercials 504,506, 508 are of different lengths are relatively short (e.g., less thana minute long, etc.). In the illustrated example of FIG. 5A, the queryfingerprints 505, 507, 509 were generated using the query fingerprintgenerator 108 by analyzing the audio associated with the media stream500. In other examples, the query fingerprints 505, 507, 509 can begenerated by any other suitable means.

The example reference fingerprints 510, 512, 514 are referencefingerprints stored in the reference fingerprint database 116. In theillustrated example of FIG. 5A, the reference fingerprints 510, 512, 514were generated from the commercials 504, 506, 508, respectively, (e.g.,provides by the advertisers, retrieved from a database, etc.) and notfrom media stream 500. The reference fingerprints 510, 512, 514 weregenerated using the reference fingerprint generator 120. In otherexamples, the reference fingerprints 510, 512, 514 can be generated byany other suitable means.

The content change points 518A, 518B, 518C, 518D represent the portionsof the media stream where the media content changes. That is, the firstcontent change point 518A represents the transition point between themedia 502 and the beginning of the first commercial 504, the secondcontent change point 518B represents the transition point between theend of the first commercial 504 and the beginning of the secondcommercial 506, the third content change point 518C represents thetransition point between the end of the second commercial 506 and thebeginning of the third commercial 508, and the fourth content changepoint 518D represents the transition point between the end of the thirdcommercial 508 and the media 502. Because each subfingerprint of thequery fingerprints 505, 507, 509 is generated by normalizing local audiocharacteristics (e.g., energy extrema, etc.), the subfingerprints of thequery fingerprints 505, 507, 509 associated with the portions of thecommercials 504, 506, 508, respectively, near the content change points518A, 518B, 518C, 518D are normalized partly by audio characteristics ofadjacent media. For example, the subfingerprints of the first queryfingerprint 505 near the first content change point 518A are calculatedpartly based on the audio characteristics of the media 502, thesubfingerprints of the second query fingerprint 507 near the firstcontent change point 518A are partly calculated based the audiocharacteristics of the first commercial 504, etc. Accordingly, thesubfingerprints of the query fingerprints 505, 507, 509 associated withthe portions of the commercials 504, 506, 508 near the content changepoints 518A, 518B, 518C, 518D may not match the correspondingsubfingerprints of the reference fingerprints 510, 512, 514 despitebeing generated from the commercials 504, 506, 508.

The arrangement of commercials (e.g., the commercials 504, 506, 508,etc.) displayed during broadcasts is variable. That is, the mediapreceding and proceeding the first commercial 504, the second commercial506, and/or the third commercial 508 can vary depending on the time ofbroadcast and the broadcasting channel and can be decided by the contentprovider. As such, the subfingerprints of the generated queryfingerprints from the commercials 504, 506, 508 can change depending onthe media immediately proceeding and preceding each of the commercials504, 506, 508. As such, the likelihood of successfully matching thequery fingerprints 505, 507, 509 to the reference fingerprints 510, 512,514 can be inhibited.

FIG. 5B is the content of an example audio signal 524 including exampletuning events 525A, 525B, 525C, 525D that can be processed by the system100 of FIG. 1. In the illustrated example of FIG. 5B, the audio signal524 includes media associated with an example first channel 526A, anexample second channel 526B, and an example third channel 526C. Theaudio signal 524 is processed to generated example query fingerprints528 (e.g., by the system 100 of FIG. 1, etc.) composed of an examplefirst query fingerprint portion 530A, an example second queryfingerprint portion 530B, an example third query fingerprint portion530C, and example fourth query fingerprint portion 530D, which aredelineated by the tuning events 525A, 525B, 525C, 525D.

The audio signal 524 is composed of media from multiple channels 526A,526B, 526C. For example, the audio signal 524 can be generated by a userchanging (e.g., tuning, etc.) a media device (e.g., a television, aradio, a portable audio device, etc.) between multiple channels. In someexamples, the multiple channels 526A, 526B, 526C represent differentmedia broadcasts (e.g., a broadcast from a new channel, a broadcast froma specific sports channel, a specific radio station, etc.). In otherexamples, the multiple channels 526A, 526B, 526C are different specificpieces of media (e.g., a first movie, a second movie, a third movie,etc.). In some examples, the reference fingerprints corresponding to themedia of the channels 526A, 526B, 526C are generated by directlyprocessing the unbroken stream (e.g., without tuning events, etc.) ofthe multiple channels 526A, 526B, 526C. Each time the user switchesbetween the channels 526A, 526B, 526C, one of the tuning events 525A,525B, 525C, 525D occurs. For example, at the example first tuning event525A, the media associated with the audio signal 524 switches from thesecond channel 526B to the third channel 526C. While the illustratedexample of FIG. 5B is only described with reference to three channelsand four tuning events, other examples can include any suitable numberof channels and tuning events.

The example query fingerprint portions 530A, 530B, 530C, 530D, 530E ofthe query fingerprints 528 corresponds to the portions of the audiosignal 524 delineated by the tuning events 525A, 525B, 525C, 525D. Thefirst query fingerprint portion 530A corresponds to the portion of theaudio signal 524 before the first tuning event 525A. The second queryfingerprint portion 530B corresponds to the portion of the audio signalbetween the first tuning event 525A and the second tuning event 525B.The third query fingerprint portion 530C corresponds to the portion ofthe audio signal 524 between the second tuning event 525B and the thirdturning event 525C. The fourth query fingerprint portion 530Dcorresponds to the portion of the audio signal 524 between the thirdtuning event 525C and the fourth tuning event 525D. The subfingerprintsof the first query fingerprint portion 530A and fourth query fingerprintportion 530D can be used to identify the media associated with thesecond channel 526B. The subfingerprints of the second query fingerprintportion 530B and the fifth query finger portion 530BE can be used toidentify the media associated with the third channel 526C. Thesubfingerprints of the third query fingerprint portion 530C can be usedto identify the media associated with the first channel 526A.

Because each subfingerprint of the query fingerprints 528 is generatedby normalizing local audio characteristics (e.g., energy extrema, etc.),the subfingerprints of the query fingerprints 528 near the tuning events525A, 525B, 525C, 525D (e.g., near the beginning or end of each of thequery fingerprint portions 530A, 530B, 530C, 530D, 530E, etc.) arenormalized partly by audio characteristics of media on channels notcorresponding to the actual channel associated with the queryfingerprint portions 530A, 530B, 530C, 530D, 530E. For example, thesubfingerprints of the query fingerprint portions 530A near the firstturning event 525B are normalized partly by the audio characteristics ofmedia associated with the third channel 526C, despite the first queryfingerprint portions 530A identifying the media on the second channel526B. Accordingly, the subfingerprints of the query fingerprints 528associated with the portions of the audio signal 524 near the tuningevents 525A, 525B, 525C, 525D may not match the correspondingsubfingerprints of the reference fingerprints identifying the media ofthe audio channels 526A, 526B, 526C despite being generated from thesame reference media.

The location of tuning events (e.g., the tuning events 525A, 525B, 525C,525D, etc.) in an audio signal are generated by the media consumption ofa user. As such, the audio signal 524 is user-determined and notdirectly identifiable by a monitoring entity. That is, the location oftuning events 525A, 525B, 525C, 525D can be difficult to identify basedon the generated query fingerprints (e.g., the query fingerprints 528,etc.). The subfingerprints of the generated query fingerprints 528 fromthe audio signal 524 can change based on the location of the tuningevents. As such, the likelihood of successfully matching the queryfingerprints 528 to the corresponding reference fingerprints can beinhibited.

FIG. 6 is an illustration showing an example generation 600 ofalternative subfingerprints output by the query fingerprint generator108 and/or the reference fingerprint generator 120 of FIGS. 1, 2, and/or3. In the illustrated example of FIG. 6, an example audio signal 602divided into signal portions including an example first audio signalportion 604A and an example second audio signal portion 604B. In theillustrated example of FIG. 6, the audio signal portion 604A isprocessed (e.g., by the query fingerprint generator 108, by thereference fingerprint generator 120, etc.) to generate an exampleprimary subfingerprint 606, an example first secondary subfingerprint608, and an example second secondary subfingerprint 610 having anexample first subfingerprint portions 612, an example secondsubfingerprint portions 614, and an example third subfingerprintportions 616. Each of the primary subfingerprints 606 and firstsecondary subfingerprint 608, and the second secondary subfingerprint610 is composed of strong portions (illustrated as black rectangles),neutral portions (illustrated as dot-shaded rectangles), and weakportions (illustrated as white rectangles, etc.). While the illustratedexample of FIG. 6 only includes the first secondary subfingerprint 608and the second secondary subfingerprint 610, in other examplesadditional subfingerprints can be generated.

The example primary subfingerprint 606 includes (e.g., is composed of,etc.) the example first subfingerprints portions 612. The firstsubfingerprint portions 612 correspond to the specific time-frequencybins of the first audio signal portion 604A that are energy extremaselected (e.g., by the subfingerprint generator 212 of FIGS. 2 and/or 3,etc.) after the audio signal portion 604A has been normalized. In someexamples, each of the first subfingerprint portions 612 is a datastructure (e.g., a bit, a byte, etc.) corresponding to the location ofthe time-frequency bin of the spectrogram selected to form part of theprimary subfingerprint 606. In the illustrated example of FIG. 6, theportion strength evaluator 214 of FIGS. 2 and/or 3 has analyzed each ofthe first subfingerprint portions 612 to determine the strength of eachportion of the first subfingerprints portions 612. For example, theportion strength evaluator 214 can overlay white noise onto the audiosignal portion 604A and regenerate the subfingerprint. Additionally oralternatively, the portion strength evaluator 214 can append differentaudio (e.g., white noise, different media, etc.) before or after theaudio signal portion 604A. In such examples, the portion strengthevaluator 214 can determine which of the first subfingerprint portions612 are more likely to change in response to different adjacent audioand/or noise (e.g., comparing the percent of changes to a threshold,comparing the number of changes to a threshold, etc.),

In the illustrated example of FIG. 6, the portion strength evaluator 214has identified some of the subfingerprint portions 612 as strongfingerprints, including an example strong subfingerprint portion 618,some of the subfingerprint portions 612 as neutral fingerprints,including an example neutral subfingerprint 620, and some of thesubfingerprint portions 612 as weak subfingerprint portions, includingan example weak subfingerprint portion 622. In the illustrated exampleof FIG. 6, the portion replacer 216 replaces the identified weakportions of the subfingerprint portions 612 with alternativesubfingerprint portions. In the illustrated example of FIG. 6, theportion replacer 216 has replaced the weak subfingerprint portion 622with an example first alternative portion 624 to generate the firstsecondary subfingerprint 608. The portion replacer 216 has replaced theweak subfingerprint portion 622 with an example second alternativeportion 626 to generate the second secondary subfingerprint 610.Additionally or alternatively, the portion replacer 216 can replaceadditional portions of the subfingerprint portions 612 to generate thesecondary fingerprints 608, 610. In some examples, the portion replacer216 can generate additional secondary fingerprints.

If the primary subfingerprint 606, the first secondary subfingerprint608, and the second secondary subfingerprint 610 are generated by thequery fingerprint generator 108, each of the primary subfingerprint 606,the first secondary subfingerprint 608, and the second secondarysubfingerprint 610 can be used to generate a fingerprint for the audiosignal 602, which can then be compared by the fingerprint comparator 114to stored reference fingerprints in the reference fingerprint database116 to identify the audio signal 602. In some examples, the otherportions of the audio signal 602 can be similarly processed by the queryfingerprint generator 108 to generate alternative subfingerprints foreach of those other portions. In other examples, only the boundarysegments of the audio signal 602 (e.g., the audio signal portions 604A,604B) can be processed by query fingerprint generator 108 to generatealternative fingerprints including various combinations of the generatedsubfingerprints.

If the primary subfingerprint 606, the first secondary subfingerprint608, and the second secondary subfingerprint 610 are generated by thereference fingerprint generator 120, each of the primary subfingerprint606, the first secondary subfingerprint 608, and the second secondarysubfingerprint 610 can be used to generate a fingerprint for the audiosignal 602, which can then be compared by the fingerprint comparator 114to received query fingerprints. In some examples, the other portions ofthe audio signal 602 can be similarly processed by the referencefingerprint generator 120 to generate alternative subfingerprints foreach of those other portions. In other examples, only the boundarysegments of the audio signal 602 (e.g., the audio signal portions 604A,604B) can be processed by reference fingerprint generator 120 togenerate alternative fingerprints including various combinations of thegenerated subfingerprints. In such examples, each of the alternativefingerprints is stored in the database 116 and can be used to generatethe alternative reference. As such employment of the system 100 of FIG.1 can be used to minimize the matching difficulties arising from thetuning events of FIG. 5B and the channel change events of FIG. 5A.

A flowchart representative of example hardware logic, machine readableinstructions, hardware implemented state machines, and/or anycombination thereof for implementing the query fingerprint generator 108of FIG. 2 is shown in FIG. 7. The machine readable instructions may beone or more executable programs or portion(s) of an executable programfor execution by a computer processor and/or processor circuitry, suchas the processor 912 shown in the example processor platform 900discussed below in connection with FIG. 9. The program may be embodiedin software stored on a non-transitory computer readable storage mediumsuch as a CD-ROM, a floppy disk, a hard drive, a DVD, a Blu-ray disk, ora memory associated with the processor 912, but the entire programand/or parts thereof could alternatively be executed by a device otherthan the processor 912 and/or embodied in firmware or dedicatedhardware. Further, although the example program is described withreference to the flowchart illustrated in FIG. 9, many other methods ofimplementing the example query fingerprint generator 108 mayalternatively be used. For example, the order of execution of the blocksmay be changed, and/or some of the blocks described may be changed,eliminated, or combined. Additionally or alternatively, any or all ofthe blocks may be implemented by one or more hardware circuits (e.g.,discrete and/or integrated analog and/or digital circuitry, an FPGA, anASIC, a comparator, an operational-amplifier (op-amp), a logic circuit,etc.) structured to perform the corresponding operation withoutexecuting software or firmware. The processor circuitry may bedistributed in different network locations and/or local to one or moredevices (e.g., a multi-core processor in a single machine, multipleprocessors distributed across a server rack, etc).

The process 700 of FIG. 7 includes block 702. At block 702, the audiosignal interface 202 receives the reference audio signal 118. In someexamples, the reference audio signal interface 302 receives a digitizedreference audio signal 118 (e.g., actual audio captured by a microphone,transferred over a network, etc.). In other examples, the audio signalinterface 202 can request the reference audio signal 118 from adatabase. In some examples, the audio signal interface 202 can includean analog-to-digital converter to convert the audio into the referenceaudio signal 118.

At block 704, the audio segmenter 204 divides the reference audio signal118 into segments. For example, the audio segmenter 204 can divide thereference audio signal 118 into temporal segments corresponding to alength of the reference audio signal 118 associated with a sample (e.g.,the period of the reference audio signal 118 corresponding to asubfingerprint, etc.). In some examples, the audio segmenter 204 cansegment the reference audio signal 118 into audio segments intocorresponding to the length of a time bin (e.g., a frame, etc.).

At block 706, the signal transformer 206 transforms the reference audiosignal 118 into the frequency domain to generate time-frequency bins.For example, the signal transformer 206 can transform the portion of thereference audio signal 118 corresponding to the audio segment using aFast Fourier Transform (FFT). In other examples, the signal transformer206 can use any other suitable means of transforming the reference audiosignal 118 (e.g., discrete Fourier transform, a sliding time windowFourier transform, a wavelet transform, a discrete Hadamard transform, adiscrete Walsh Hadamard, a discrete cosine transform, etc.). In someexamples, the time-frequency bins generated by the signal transformer206 and corresponding to the selected audio segment are associated withthe intersection of each frequency bin of the reference audio signal 118and the time bin(s) associated with the audio segment. In some examples,each time-frequency bin generated by the audio segmenter 204 has anassociated magnitude value (e.g., a magnitude of the FFT coefficient ofthe reference audio signal 118 associated with that time-frequency bin,etc.).

At block 708, the audio segmenter 204 selects an audio segment. Forexample, the audio segmenter 204 can select a first audio segment (e.g.,the audio segment corresponding to the beginning of the reference audiosignal 118, etc.). In some examples, the audio segmenter 204 can selectan audio segment temporally immediately adjacent to a previouslyselected audio segment. In other examples, the audio segmenter 204 canselect an audio segment based on any suitable characteristic. In someexamples, the audio segmenter 204 windows the first segment.

At block 710, the audio characteristic determiner 208 determines theaudio characteristic of each time-frequency bin in the audio segment.For example, the audio characteristic determiner 208 can determine themagnitude of each time-frequency bin in the audio segment. In suchexamples, the audio characteristic determiner 208 can calculate theenergy and/or the entropy associated with each time-frequency bin. Inother examples, the audio characteristic determiner 208 can determineany other suitable audio characteristic(s) (e.g., amplitude, power,etc.).

At block 712, the bin normalizer 210 normalizes each time-frequency binbased on an average audio-characteristic of the surrounding audioregion. For example, the bin normalizer 210 can normalize an exampletime-frequency bin (e.g., the first time-frequency bin 404, etc.) basedon the average audio characteristic of the surrounding region (e.g., thefirst region 406, etc.) as determined during the execution of block 710.In some examples, the bin normalizer generates a normalized spectrogram(e.g., the normalized spectrogram 416 of FIG. 4B, etc.) by normalizingeach of the time-frequency bins of the audio segment.

At block 714, the subfingerprint generator 212 computes the primarysubfingerprint(s) associated with the audio segment. For example, thesubfingerprint generator 212 can generate a subfingerprint based on thenormalized values of the time-frequency bins of the previous segment(s)analyzed at block 712. In some examples, the subfingerprint generator212 generates a subfingerprint by selecting energy and/or entropyextrema (e.g., five extrema, 20 extrema, etc.) in the previoussegment(s). In such examples, the subfingerprint generated by thesubfingerprint generator 212 includes portions (e.g., bits, etc.)corresponding to each one of the selected extrema. In such examples,each portion of a generated subfingerprint corresponds to the locationof an energy extremum. In some examples, the subfingerprint generator212 does not generate a subfingerprint (e.g., the previous audio segmentis not being used to subfingerprint due to down-sampling, etc.). In suchexamples, blocks 716-820 are not executed for this selected segment.

At block 716, the portion strength evaluator 214 determines the strengthof each portion of the generated subfingerprint. For example, theportion strength evaluator 214 can repeat the subfingerprint generatorprocess (e.g., the execution of blocks 710-714, etc.) but overlaying theaudio signal with random noise (e.g., white noise, artificiallygenerated background audio, etc.). In some examples, because thesubfingerprints associated with each audio sample depend on audiocharacteristics of adjacent samples, the portion strength evaluator 214can determine the strength of portions of a subfingerprint by changingthe audio characteristics of adjacent audio samples. In some suchexamples, the portion strength evaluator 214 can replace adjacent audiosegments with different audio segments and/or append different audio onthe audio segment being analyzed. Additionally or alternatively, theportion strength evaluator 214 can, for some or all samples of the audiosignal, replace the adjacent audio samples with different audio (e.g.,white noise, artificially generated background audio, different media,etc.). Based on the frequency of the portions of the generatedsubfingerprints change, the portion strength evaluator 214 can determinethe strength of each portion as “weak,” “strong,” or “neutral.” In someexamples, the portion strength evaluator 214 can compare the frequencyof change to a threshold.

At block 718, the portion replacer 216 replaces reference weak portionsof subfingerprints with alternative portions. For example, the portionreplacer 216 can replace weak portions of generated subfingerprints withrandom audio. In such examples, the portion replacer 216 can replacesome or all of the identified weak portions with a random portion. Forexample, the portion replacer 216 can replace the weak portions withaudio generated during the operation of the portion strength evaluator214. In other examples, the portion replace 216 can replace theidentified weak portions with any other suitable portion.

At block 720, the audio segmenter 204 determines if another segment isto be selected. For example, the audio segmenter 204 can determine ifthere are additional audio segments of the reference audio signal 118that have yet to be analyzed. If another segment is to be selected bythe audio segmenter 204, the process 700 returns to block 706. Ifanother segment is not to be selected by the audio segmenter 204, theprocess 700 advances to block 722.

At block 722, the fingerprint generator 218 generates fingerprint(s)based on generated subfingerprint(s). For example, the fingerprintgenerator 218 can generate the query fingerprint(s) 110 based on thesubfingerprints generated by the subfingerprint generator 212. Forexample, the fingerprint generator 218 can concatenate thesubfingerprints associated with each audio segment into the queryfingerprint(s) 110. In some examples, the fingerprint generator 218 cangenerate a fingerprint including the subfingerprints in which the weakportions have been replaced by the portion replacer 216. In someexamples, the fingerprint generator 218 can generate multiple queryfingerprints based on the portions of the subfingerprints. In suchexamples, the fingerprint generator 218 can generate fingerprintsincluding different subfingerprints of which the weak portions have beenreplaced. In some examples, the portion replacer 216 can be omitted. Insome such examples, the fingerprint generator 218 can generate multiplefingerprints based on different audio overlays and/or audio sampleappendages. In some such examples, the fingerprint generator 218 cancause the identified weak portions to be included from the queryfingerprint 110 when the query fingerprint 110 is compared to referencefingerprints by the fingerprint comparator 114.

At block 724, the fingerprint generator 218 transmits generated queryfingerprint(s) 110 to the central facility 112. For example, thefingerprint generator 218 can transmit the generated query fingerprintvia the network 111. In other examples, the fingerprint generator 218can transmit the generated query fingerprint(s) 110 via a wiredconnection and/or any other suitable connection. The process 700 ends.

A flowchart representative of example hardware logic, machine readableinstructions, hardware implemented state machines, and/or anycombination thereof for implementing the reference fingerprint generator120 of FIG. 3 is shown in FIG. 8. The machine readable instructions maybe one or more executable programs or portion(s) of an executableprogram for execution by a computer processor and/or processorcircuitry, such as the processor 1012 shown in the example processorplatform 900 discussed below in connection with FIG. 10. The program maybe embodied in software stored on a non-transitory computer readablestorage medium such as a CD-ROM, a floppy disk, a hard drive, a DVD, aBlu-ray disk, or a memory associated with the processor 1012, but theentire program and/or parts thereof could alternatively be executed by adevice other than the processor 1012 and/or embodied in firmware ordedicated hardware. Further, although the example program is describedwith reference to the flowchart illustrated in FIG. 10, many othermethods of implementing the example reference fingerprint generator 120may alternatively be used. For example, the order of execution of theblocks may be changed, and/or some of the blocks described may bechanged, eliminated, or combined. Additionally or alternatively, any orall of the blocks may be implemented by one or more hardware circuits(e.g., discrete and/or integrated analog and/or digital circuitry, anFPGA, an ASIC, a comparator, an operational-amplifier (op-amp), a logiccircuit, etc.) structured to perform the corresponding operation withoutexecuting software or firmware. The processor circuitry may bedistributed in different network locations and/or local to one or moredevices (e.g., a multi-core processor in a single machine, multipleprocessors distributed across a server rack, etc.).

The process 800 of FIG. 8 includes block 802. At block 802, thereference audio signal interface 302 receives the digitized audio signal106. For example, the reference audio signal interface 302 can receiveaudio (e.g., emitted by the audio source 102 of FIG. 1, etc.) capturedby the microphone 104. In this example, the microphone can include ananalog to digital converter to convert the audio into a digitized audiosignal 106. In other examples, the reference audio signal interface 302can receive audio stored in a database (e.g., the volatile memory 1014of FIG. 10, the non-volatile memory 1016 of FIG. 10, the mass storage1028 of FIG. 10, etc.). In other examples, the digitized audio signal106 can be transmitted to the reference audio signal interface 302 overa network 111. Additionally or alternatively, the reference audio signalinterface 302 can receive the audio signal 106 by any other suitablemeans.

At block 804, the audio segmenter 204 divides audio signal 106 intosegments. For example, the audio segmenter 204 can divide the audiosignal 106 into temporal segments corresponding to a length of the audiosignal 106 associated with a sample (e.g., the period of the audiosignal 106 corresponding to a subfingerprint, etc.). In some examples,the audio segmenter 204 can segment the audio signal 106 into audiosegments corresponding to the length of a time bin (e.g., a frame,etc.).

At block 806, the signal transformer 206 transforms the audio signalinto the frequency domain to generate time-frequency bins. For example,the signal transformer 206 can transform the portion of the audio signal106 corresponding to the audio segment using a Fast Fourier Transform(FFT). In other examples, the signal transformer 206 can use any othersuitable means of transforming the audio signal 106 (e.g., discreteFourier transform, a sliding time window Fourier transform, a wavelettransform, a discrete Hadamard transform, a discrete Walsh Hadamard, adiscrete cosine transform, etc.). In some examples, the time-frequencybins generated by the signal transformer 206 and corresponding to theselected audio segment are associated with the intersection of eachfrequency bin of the audio signal 106 and the time bin(s) associatedwith the audio segment. In some examples, each time-frequency bingenerated by the audio segmenter 204 has an associated magnitude value(e.g., a magnitude of the FFT coefficient of the audio signal 106associated with that time-frequency bin, etc.).

At block 808, the audio characteristic determiner 208 determines theaudio characteristic of each time-frequency bin in the audio segment.For example, the audio characteristic determiner 208 can determine themagnitude of each time-frequency bin in the audio segment. In suchexamples, the audio characteristic determiner 208 can calculate theenergy and/or the entropy associated with each time-frequency bin. Inother examples, the audio characteristic determiner 208 can determineany other suitable audio characteristic(s) (e.g., amplitude, power,etc.).

At block 810, the bin normalizer 210 normalizes each time-frequency binbased on an average audio-characteristic of the surrounding audioregion. For example, the bin normalizer 210 normalizes eachtime-frequency bin based on an average audio-characteristic ofsurrounding audio region. For example, the bin normalizer 210 cannormalize an example time-frequency bin (e.g., the first time-frequencybin 404, etc.) based on the average audio characteristic of thesurrounding region (e.g., the first region 406, etc.) as determinedduring the execution of block 710. In some examples, the bin normalizergenerates a normalized spectrogram (e.g., the normalized spectrogram 416of FIG. 4B, etc.) by normalizing each of the time-frequency bins ofaudio segment.

At block 812, the audio segmenter 204 selects an audio segment. Forexample, the audio segmenter 204 can select a first audio segment (e.g.,the audio segment corresponding to the beginning of the audio signal106, etc.). In some examples, the audio segmenter 204 can select anaudio segment temporally immediately adjacent to a previously selectedaudio segment. In other examples, the audio segmenter 204 can select anaudio segment based on any suitable characteristic. In some examples,the audio segmenter windows the first segment.

At block 814, the subfingerprint generator 212 computes primarysubfingerprint(s) associated with the audio segment. For example, thesubfingerprint generator 212 can generate a subfingerprint based on thenormalized values of the time-frequency bins of the previous segment(s)analyzed at block 812. In some examples, the subfingerprint generator212 generates a subfingerprint by selecting energy and/or entropyextrema (e.g., five extrema, 20 extrema, etc.) in the previoussegment(s). In such examples, the subfingerprint generated by thesubfingerprint generator 212 includes portions (e.g., bits, etc.)corresponding to each one of the selected extrema. In such examples,each portion of a generated subfingerprint corresponds to the locationof an energy extremum. In some examples, the subfingerprint generator212 does not generate a subfingerprint (e.g., the previous audio segmentis not being used to subfingerprint due to down-sampling, etc.). In suchexamples, blocks 816-720 are not executed for this selected segment.

At block 816, the subfingerprint generator 212 determines if analternative subfingerprint is to be generated. For example, thesubfingerprint generator 212 can determine if a user has requested analternative subfingerprint be generated. Additionally or alternatively,the subfingerprint generator 212 can determine if an alternativefingerprint is to be generated by any other suitable means. If analternative subfingerprint is to be generated, the process 800 advancesto block 818. If an alternative subfingerprint is not to be generated,the process 800 advances to block 722.

At block 818, the portion strength evaluator 214 determines the strengthof each portion of subfingerprint. For example, the portion strengthevaluator 214 can repeat the subfingerprint generator process (e.g., theexecution of blocks 806-814, etc.) but overlaying the audio signal withrandom noise (e.g., white noise, artificially generated backgroundaudio, etc.). In some examples, because the subfingerprints associatedwith each audio sample depend on audio characteristics of adjacentsamples, the portion strength evaluator 214 can determine the strengthof portions of a subfingerprint by changing the audio characteristics ofadjacent audio samples. In some such examples, the portion strengthevaluator 214 can replace adjacent audio segments with different audiosegments and/or append different audio on the audio segment beinganalyzed. Additionally or alternatively, the portion strength evaluator214 can, for some or all samples of the audio signal, replace theadjacent audio samples with different audio (e.g., white noise,artificially generated background audio, different media, etc.). Basedon the frequency of the portions of the generated subfingerprintschange, the portion strength evaluator 214 can determine the strength ofeach portion as “weak,” “strong,” or “neutral.” In some examples, theportion strength evaluator 214 can compare the frequency of change to athreshold.

At block 820, the portion replacer 216 replaces weak portions withalternative portions. For example, the portion replacer 216 can replaceweak portions of generated subfingerprints with random audio. In suchexamples, the portion replacer 216 can replace some or all of theidentified weak portions with a random portion. For example, the portionreplacer 216 can replace the weak portions with audio generated duringthe operation of the portion strength evaluator 214. In other examples,the portion replacer 216 can replace the identified weak portions withany other suitable portion.

At block 822, the audio segmenter 204 determines if another segment isto be selected. For example, the audio segmenter 204 can determine ifthere are additional audio segments of the audio signal 106 that haveyet to be analyzed. If another segment is to be selected by the audiosegmenter 204, the process 800 returns to block 812. If another segmentis not to be selected by the audio segmenter 204, the process 800advances to block 824.

At block 824, the reference fingerprint generator 304 generatesreference fingerprint(s) 121 for audio signal based on determinedprimary and alternative subfingerprints. For example, the referencefingerprint generator 304 can generate the reference fingerprint(s) 121based on the subfingerprints generated by the subfingerprint generator212. For example, the reference fingerprint generator 304 canconcatenate the subfingerprints associated with each audio segment intothe reference fingerprint(s) 118. In some examples, the referencefingerprint generator 304 can generate a fingerprint including thesubfingerprints in which the weak portions have been replaced by theportion replacer 216. In some examples, the reference fingerprintgenerator 304 can generate multiple query fingerprints based on theportions of the subfingerprints. In such examples, the referencefingerprint generator 304 can generate fingerprints including differentsubfingerprints of which the weak portions have been replaced. In someexamples, the portion replacer 216 can be omitted. In some suchexamples, the reference fingerprint generator 304 can generate multiplefingerprints based on different audio overlays and/or audio sampleappendages. In some such examples, the reference fingerprint generator304 can cause the identified weak portions to be included from the queryfingerprint 110 when the reference fingerprint 121 is compared toreference fingerprints by the fingerprint comparator 114.

At block 826, the fingerprint generator 218 adds the generated referencefingerprint(s) 121 to the reference fingerprint database 116. Forexample, the fingerprint generator 218 can transmit and/or transmit thegenerated reference fingerprint(s) 121 to the reference fingerprintdatabase 116 via a wireless network. In other examples, the fingerprintgenerator 218 can transfer the generated reference fingerprint(s) to thereference fingerprint database 116 via a wired connection and/or anyother suitable means. The process 800 then ends.

The machine readable instructions described herein may be stored in oneor more of a compressed format, an encrypted format, a fragmentedformat, a compiled format, an executable format, a packaged format, etc.Machine readable instructions as described herein may be stored as dataor a data structure (e.g., portions of instructions, code,representations of code, etc.) that may be utilized to create,manufacture, and/or produce machine executable instructions. Forexample, the machine readable instructions may be fragmented and storedon one or more storage devices and/or computing devices (e.g., servers)located at the same or different locations of a network or collection ofnetworks (e.g., in the cloud, in edge devices, etc.). The machinereadable instructions may require one or more of installation,modification, adaptation, updating, combining, supplementing,configuring, decryption, decompression, unpacking, distribution,reassignment, compilation, etc. in order to make them directly readable,interpretable, and/or executable by a computing device and/or othermachine. For example, the machine readable instructions may be stored inmultiple parts, which are individually compressed, encrypted, and storedon separate computing devices, wherein the parts when decrypted,decompressed, and combined form a set of executable instructions thatimplement one or more functions that may together form a program such asthat described herein.

In another example, the machine readable instructions may be stored in astate in which they may be read by processor circuitry, but requireaddition of a library (e.g., a dynamic link library (DLL)), a softwaredevelopment kit (SDK), an application programming interface (API), etc.in order to execute the instructions on a particular computing device orother device. In another example, the machine readable instructions mayneed to be configured (e.g., settings stored, data input, networkaddresses recorded, etc.) before the machine readable instructionsand/or the corresponding program(s) can be executed in whole or in part.Thus, machine readable media, as used herein, may include machinereadable instructions and/or program(s) regardless of the particularformat or state of the machine readable instructions and/or program(s)when stored or otherwise at rest or in transit.

The machine readable instructions described herein can be represented byany past, present, or future instruction language, scripting language,programming language, etc. For example, the machine readableinstructions may be represented using any of the following languages: C,C++, Java, C#, Perl, Python, JavaScript, HyperText Markup Language(HTML), Structured Query Language (SQL), Swift, etc.

As mentioned above, the example processes of FIGS. 7 and 8 may beimplemented using executable instructions (e.g., computer and/or machinereadable instructions) stored on a non-transitory computer and/ormachine readable medium such as a hard disk drive, a flash memory, aread-only memory, a compact disk, a digital versatile disk, a cache, arandom-access memory and/or any other storage device or storage disk inwhich information is stored for any duration (e.g., for extended timeperiods, permanently, for brief instances, for temporarily buffering,and/or for caching of the information). As used herein, the termnon-transitory computer readable medium is expressly defined to includeany type of computer readable storage device and/or storage disk and toexclude propagating signals and to exclude transmission media.

“Including” and “comprising” (and all forms and tenses thereof) are usedherein to be open ended terms. Thus, whenever a claim employs any formof “include” or “comprise” (e.g., comprises, includes, comprising,including, having, etc.) as a preamble or within a claim recitation ofany kind, it is to be understood that additional elements, terms, etc.may be present without falling outside the scope of the correspondingclaim or recitation. As used herein, when the phrase “at least” is usedas the transition term in, for example, a preamble of a claim, it isopen-ended in the same manner as the term “comprising” and “including”are open ended. The term “and/or” when used, for example, in a form suchas A, B, and/or C refers to any combination or subset of A, B, C such as(1) A alone, (2) B alone, (3) C alone, (4) A with B, (5) A with C, (6) Bwith C, and (7) A with B and with C. As used herein in the context ofdescribing structures, components, items, objects and/or things, thephrase “at least one of A and B” is intended to refer to implementationsincluding any of (1) at least one A, (2) at least one B, and (3) atleast one A and at least one B. Similarly, as used herein in the contextof describing structures, components, items, objects and/or things, thephrase “at least one of A or B” is intended to refer to implementationsincluding any of (1) at least one A, (2) at least one B, and (3) atleast one A and at least one B. As used herein in the context ofdescribing the performance or execution of processes, instructions,actions, activities and/or steps, the phrase “at least one of A and B”is intended to refer to implementations including any of (1) at leastone A, (2) at least one B, and (3) at least one A and at least one B.Similarly, as used herein in the context of describing the performanceor execution of processes, instructions, actions, activities and/orsteps, the phrase “at least one of A or B” is intended to refer toimplementations including any of (1) at least one A, (2) at least one B,and (3) at least one A and at least one B.

As used herein, singular references (e.g., “a,” “an,” “first,” “second,”etc.) do not exclude a plurality. The term “a” or “an” entity, as usedherein, refers to one or more of that entity. The terms “a” (or “an”),“one or more,” and “at least one” can be used interchangeably herein.Furthermore, although individually listed, a plurality of means,elements or method actions may be implemented by, e.g., a single unit orprocessor. Additionally, although individual features may be included indifferent examples or claims, these may possibly be combined, and theinclusion in different examples or claims does not imply that acombination of features is not feasible and/or advantageous.

FIG. 9 is a block diagram of an example processor platform 1000structured to execute the instructions of FIG. 7 to implement the queryfingerprint generator 108 of FIG. 2. The processor platform 900 can be,for example, a server, a personal computer, a workstation, aself-learning machine (e.g., a neural network), a mobile device (e.g., acell phone, a smart phone, a tablet such as an iPad™), a personaldigital assistant (PDA), an Internet appliance, a DVD player, a CDplayer, a digital video recorder, a Blu-ray player, a gaming console, apersonal video recorder, a set top box, a headset or other wearabledevice, or any other type of computing device.

The processor platform 900 of the illustrated example includes aprocessor 912. The processor 912 of the illustrated example is hardware.For example, the processor 912 can be implemented by one or moreintegrated circuits, logic circuits, microprocessors, GPUs, DSPs, orcontrollers from any desired family or manufacturer. The hardwareprocessor may be a semiconductor based (e.g., silicon based) device. Inthis example, the processor implements the example audio signalinterface 202, the example audio segmenter 204, the example signaltransformer 206, the example audio characteristic determiner 208, theexample bin normalizer 210, the example subfingerprint generator 212,the example portion strength evaluator 214, the example portion replacer216, and the example fingerprint generator 218.

The processor 912 of the illustrated example includes a local memory 913(e.g., a cache). The processor 912 of the illustrated example is incommunication with a main memory including a volatile memory 914 and anon-volatile memory 916 via a bus 918. The volatile memory 914 may beimplemented by Synchronous Dynamic Random Access Memory (SDRAM), DynamicRandom Access Memory (DRAM), RAMBUS® Dynamic Random Access Memory(RDRAM®) and/or any other type of random access memory device. Thenon-volatile memory 916 may be implemented by flash memory and/or anyother desired type of memory device. Access to the main memory 914, 916is controlled by a memory controller.

The processor platform 900 of the illustrated example also includes aninterface circuit 920. The interface circuit 920 may be implemented byany type of interface standard, such as an Ethernet interface, auniversal serial bus (USB), a Bluetooth® interface, a near fieldcommunication (NFC) interface, and/or a PCI express interface.

In the illustrated example, one or more input devices 922 are connectedto the interface circuit 920. The input device(s) 922 permit(s) a userto enter data and/or commands into the processor 912. The inputdevice(s) can be implemented by, for example, an audio sensor, amicrophone, a camera (still or video), a keyboard, a button, a mouse, atouchscreen, a track-pad, a trackball, isopoint and/or a voicerecognition system.

One or more output devices 924 are also connected to the interfacecircuit 920 of the illustrated example. The output devices 924 can beimplemented, for example, by display devices (e.g., a light emittingdiode (LED), an organic light emitting diode (OLED), a liquid crystaldisplay (LCD), a cathode ray tube display (CRT), an in-place switching(IPS) display, a touchscreen, etc.), a tactile output device, a printerand/or speaker. The interface circuit 920 of the illustrated example,thus, typically includes a graphics driver card, a graphics driver chipand/or a graphics driver processor.

The interface circuit 920 of the illustrated example also includes acommunication device such as a transmitter, a receiver, a transceiver, amodem, a residential gateway, a wireless access point, and/or a networkinterface to facilitate exchange of data with external machines (e.g.,computing devices of any kind) via a network 926. The communication canbe via, for example, an Ethernet connection, a digital subscriber line(DSL) connection, a telephone line connection, a coaxial cable system, asatellite system, a line-of-site wireless system, a cellular telephonesystem, etc.

The processor platform 900 of the illustrated example also includes oneor more mass storage devices 928 for storing software and/or data.Examples of such mass storage devices 928 include floppy disk drives,hard drive disks, compact disk drives, Blu-ray disk drives, redundantarray of independent disks (RAID) systems, and digital versatile disk(DVD) drives.

The machine executable instructions 932 of FIG. 7 may be stored in themass storage device 928, in the volatile memory 914, in the non-volatilememory 916, and/or on a removable non-transitory computer readablestorage medium such as a CD or DVD.

FIG. 10 is a block diagram of an example processor platform 1000structured to execute the instructions of FIG. 8 to implement thereference fingerprint generator 120 of FIG. 9. The processor platform1000 can be, for example, a server, a personal computer, a workstation,a self-learning machine (e.g., a neural network), a mobile device (e.g.,a cell phone, a smart phone, a tablet such as an iPad′), a personaldigital assistant (PDA), an Internet appliance, a DVD player, a CDplayer, a digital video recorder, a Blu-ray player, a gaming console, apersonal video recorder, a set top box, a headset or other wearabledevice, or any other type of computing device.

The processor platform 1000 of the illustrated example includes aprocessor 1012. The processor 1012 of the illustrated example ishardware. For example, the processor 1012 can be implemented by one ormore integrated circuits, logic circuits, microprocessors, GPUs, DSPs,or controllers from any desired family or manufacturer. The hardwareprocessor may be a semiconductor based (e.g., silicon based) device. Inthis example, the processor implements the audio signal interface 202,the example audio signal interface 202, the example audio segmenter 204,the example signal transformer 206, the example audio characteristicdeterminer 208, the example bin normalizer 210, the examplesubfingerprint generator 212, the example portion strength evaluator214, the example portion replacer 216, and the reference fingerprintgenerator 304.

The processor 1012 of the illustrated example includes a local memory1013 (e.g., a cache). The processor 1012 of the illustrated example isin communication with a main memory including a volatile memory 1014 anda non-volatile memory 1016 via a bus 1018. The volatile memory 1014 maybe implemented by Synchronous Dynamic Random Access Memory (SDRAM),Dynamic Random Access Memory (DRAM), RAMBUS® Dynamic Random AccessMemory (RDRAM®) and/or any other type of random access memory device.The non-volatile memory 1016 may be implemented by flash memory and/orany other desired type of memory device. Access to the main memory 1014,1016 is controlled by a memory controller.

The processor platform 1000 of the illustrated example also includes aninterface circuit 1020. The interface circuit 1020 may be implemented byany type of interface standard, such as an Ethernet interface, auniversal serial bus (USB), a Bluetooth® interface, a near fieldcommunication (NFC) interface, and/or a PCI express interface.

In the illustrated example, one or more input devices 1022 are connectedto the interface circuit 1020. The input device(s) 1022 permit(s) a userto enter data and/or commands into the processor 1012. The inputdevice(s) can be implemented by, for example, an audio sensor, amicrophone, a camera (still or video), a keyboard, a button, a mouse, atouchscreen, a track-pad, a trackball, isopoint and/or a voicerecognition system.

One or more output devices 1024 are also connected to the interfacecircuit 1020 of the illustrated example. The output devices 1024 can beimplemented, for example, by display devices (e.g., a light emittingdiode (LED), an organic light emitting diode (OLED), a liquid crystaldisplay (LCD), a cathode ray tube display (CRT), an in-place switching(IPS) display, a touchscreen, etc.), a tactile output device, a printerand/or speaker. The interface circuit 1020 of the illustrated example,thus, typically includes a graphics driver card, a graphics driver chipand/or a graphics driver processor.

The interface circuit 1020 of the illustrated example also includes acommunication device such as a transmitter, a receiver, a transceiver, amodem, a residential gateway, a wireless access point, and/or a networkinterface to facilitate exchange of data with external machines (e.g.,computing devices of any kind) via a network 1026. The communication canbe via, for example, an Ethernet connection, a digital subscriber line(DSL) connection, a telephone line connection, a coaxial cable system, asatellite system, a line-of-site wireless system, a cellular telephonesystem, etc.

The processor platform 1000 of the illustrated example also includes oneor more mass storage devices 1028 for storing software and/or data.Examples of such mass storage devices 1028 include floppy disk drives,hard drive disks, compact disk drives, Blu-ray disk drives, redundantarray of independent disks (RAID) systems, and digital versatile disk(DVD) drives.

The machine executable instructions 1032 of FIG. may be stored in themass storage device 1028, in the volatile memory 1014, in thenon-volatile memory 1016, and/or on a removable non-transitory computerreadable storage medium such as a CD or DVD.

Although certain example methods, apparatus and articles of manufacturehave been disclosed herein, the scope of coverage of this patent is notlimited thereto. On the contrary, this patent covers all methods,apparatus and articles of manufacture fairly falling within the scope ofthe claims of this patent.

Example methods, apparatus, systems, and articles of manufacture tofingerprint an audio signal are disclosed herein. Further examples andcombinations thereof include the following: Example 1 includes anapparatus comprising an audio segmenter to divide an audio signal into aplurality of audio segments including a first audio segment, a secondaudio segment temporally after and adjacent to the first audio segment,and a third audio segment temporally after and adjacent to the secondaudio segment, a bin normalizer to normalize the second audio segment tothereby create a first normalized audio segment, the normalization basedon first audio characteristics of the first audio segment, second audiocharacteristics of the second audio segment, and third audiocharacteristics the third audio segment, a subfingerprint generator togenerate a first subfingerprint from the first normalized audio segment,the first subfingerprint including a first portion corresponding to alocation of an energy extremum in the normalized second audio segment, aportion strength evaluator to determine a likelihood of the firstportion to change based on changes to at least one of the first audiocharacteristics, the second audio characteristics, or the third audiocharacteristics, and a portion replacer to, in response to determiningthe likelihood does not satisfy a threshold, replace the first portionwith a second portion to thereby generate a second subfingerprint.

Example 2 includes the apparatus of example 1, wherein the portionreplacer is to, in response to determining the likelihood does notsatisfy a strength threshold, exclude the first portion when matchingquery subfingerprints to the first subfingerprint.

Example 3 includes the apparatus of example 1, further including asignal transformer to transform the audio signal into a frequency domainto thereby generate a first group of time-frequency bins correspondingto the first audio segment, a second group of time-frequency binscorresponding to the second audio segment, and a third group oftime-frequency bins corresponding to the third audio segment, andwherein the normalizing of the second audio segment includes normalizinga time-frequency bin of the second group of time-frequency bins based ona surrounding region of time-frequency bins, the surrounding region oftime-frequency bins including ones of the first group of time-frequencybins and ones of the second group of time-frequency bins.

Example 4 includes the apparatus of example 1, wherein the portionstrength evaluator determines the likelihood based on changes to atleast one of the first audio characteristics, the second audiocharacteristics or the third audio characteristics by replacing thefirst audio segment with a fourth audio segment, normalizing the secondaudio segment to thereby create a second normalized audio segment basedon second audio characteristics of the fourth audio segment and thethird audio segment, generating a second subfingerprint from thenormalized second audio segment, and determining if the secondsubfingerprint includes the first portion.

Example 5 includes the apparatus of example 4, wherein the portionstrength evaluator determines the likelihood based on changes to atleast one of the first audio characteristics, the second audiocharacteristics or the third audio characteristics includes replacingthe third audio segment with a fifth audio segment, normalizing thesecond audio segment to thereby create a third normalized audio segmentbased on third audio characteristics of the first audio segment and thefifth audio segment, generating a third subfingerprint from the thirdnormalized audio segment, and determining if the second subfingerprintincludes the first portion.

Example 6 includes the apparatus of example 5, wherein at least one ofthe fourth audio segment or the fifth audio segment is randomlygenerated noise audio.

Example 7 includes the apparatus of example 4, further including afingerprint generator to store the first subfingerprint and the secondsubfingerprint to enable matching query subfingerprints to at least oneof the first subfingerprint or the second subfingerprint to therebyidentify the audio signal.

Example 8 includes a method comprising dividing an audio signal into aplurality of audio segments including a first audio segment, a secondaudio segment temporally after and adjacent to the first audio segment,and a third audio segment temporally after and adjacent to the secondaudio segment, normalizing the second audio segment to thereby create afirst normalized audio segment, the normalization based on first audiocharacteristics of the first audio segment, second audio characteristicsof the second audio segment, and third audio characteristics the thirdaudio segment, generating a first subfingerprint from the firstnormalized audio segment, the first subfingerprint including a firstportion corresponding to a location of an energy extremum in thenormalized second audio segment, determining a likelihood of the firstportion to change based on changes to at least one of the first audiocharacteristics, the second audio characteristics, or the third audiocharacteristics, and in response to determining the likelihood does notsatisfy a threshold, replacing the first portion with a second portionto thereby generate a second subfingerprint.

Example 9 includes the method of example 8, further including, inresponse to determining the likelihood does not satisfy a strengththreshold, excluding the first portion when matching querysubfingerprints to the first subfingerprint.

Example 10 includes the method of example 8, further includingtransforming the audio signal into a frequency domain to therebygenerate a first group of time-frequency bins corresponding to the firstaudio segment, a second group of time-frequency bins corresponding tothe second audio segment, and a third group of time-frequency binscorresponding to the third audio segment, and wherein the normalizingthe second audio segment includes normalizing a time-frequency bin ofthe second group of time-frequency bins based on a surrounding region oftime-frequency bins, the surrounding region of time-frequency binsincluding ones of the first group of time-frequency bins and ones of thesecond group of time-frequency bins.

Example 11 includes the method of example 8, wherein the determinationof the likelihood based on changes to at least one of the first audiocharacteristics, the second audio characteristics or the third audiocharacteristics includes replacing the first audio segment with a fourthaudio segment, normalizing the second audio segment to thereby create asecond normalized audio segment based on second audio characteristics ofthe fourth audio segment and the third audio segment, generating asecond subfingerprint from the normalized second audio segment, anddetermining if the second subfingerprint includes the first portion.

Example 12 includes the method of example 11, wherein the determinationof the likelihood based on changes to at least one of the first audiocharacteristics, the second audio characteristics or the third audiocharacteristics includes replacing the third audio segment with a fifthaudio segment, normalizing the second audio segment to thereby create athird normalized audio segment based on third audio characteristics ofthe first audio segment and the fifth audio segment, generating a thirdsubfingerprint from the third normalized audio segment, and determiningif the second subfingerprint includes the first portion.

Example 13 includes the method of example 11, further including storingthe first subfingerprint and the second subfingerprint to enablematching query subfingerprints to at least one of the firstsubfingerprint or the second subfingerprint to thereby identify theaudio signal.

Example 14 includes a non-transitory computer readable medium comprisinginstructions which, when executed, cause a processor to divide an audiosignal into a plurality of audio segments including a first audiosegment, a second audio segment temporally after and adjacent to thefirst audio segment, and a third audio segment temporally after andadjacent to the second audio segment, normalize the second audio segmentto thereby create a first normalized audio segment, the normalizationbased on first audio characteristics of the first audio segment, secondaudio characteristics of the second audio segment, and third audiocharacteristics the third audio segment, generate a first subfingerprintfrom the first normalized audio segment, the first subfingerprintincluding a first portion corresponding to a location of an energyextremum in the normalized second audio segment, determine a likelihoodof the first portion to change based on changes to at least one of thefirst audio characteristics, the second audio characteristics, or thethird audio characteristics, and in response to determining thelikelihood does not satisfy a threshold, replace the first portion witha second portion to thereby generate a second subfingerprint.

Example 15 includes the non-transitory computer readable medium ofexample 14, wherein the instructions further cause the processor to, inresponse to determining the likelihood does not satisfy a strengththreshold, excluding the first portion when matching querysubfingerprints to the first subfingerprint.

Example 16 includes the non-transitory computer readable medium ofexample 14, wherein the instructions further cause the processor totransform the audio signal into a frequency domain to thereby generate afirst group of time-frequency bins corresponding to the first audiosegment, a second group of time-frequency bins corresponding to thesecond audio segment, and a third group of time-frequency binscorresponding to the third audio segment, and wherein the normalizingthe second audio segment includes normalizing a time-frequency bin ofthe second group of time-frequency bins based on a surrounding region oftime-frequency bins, the surrounding region of time-frequency binsincluding ones of the first group of time-frequency bins and ones of thesecond group of time-frequency bins.

Example 17 includes the non-transitory computer readable medium ofexample 14, wherein the determination of the likelihood based on changesto at least one of the first audio characteristics, the second audiocharacteristics or the third audio characteristics includes replacingthe first audio segment with a fourth audio segment, normalizing thesecond audio segment to thereby create a second normalized audio segmentbased on second audio characteristics of the fourth audio segment andthe third audio segment, generating a second subfingerprint from thenormalized second audio segment, and determining if the secondsubfingerprint includes the first portion.

Example 18 includes the non-transitory computer readable medium ofexample 17, wherein the determination of the likelihood based on changesto at least one of the first audio characteristics, the second audiocharacteristics or the third audio characteristics includes replacingthe third audio segment with a fifth audio segment, normalizing thesecond audio segment to thereby create a third normalized audio segmentbased on third audio characteristics of the first audio segment and thefifth audio segment, generating a third subfingerprint from the thirdnormalized audio segment, and determining if the second subfingerprintincludes the first portion.

Example 19 includes the non-transitory computer readable medium ofexample 18, wherein at least one of the fourth audio segment or thefifth audio segment is randomly generated noise audio.

Example 20 includes the non-transitory computer readable medium ofexample 18, wherein the instructions further cause the processor tostore the first subfingerprint and the second subfingerprint to enablematching query subfingerprints to at least one of the firstsubfingerprint or the second subfingerprint to thereby identify theaudio signal. The following claims are hereby incorporated into thisDetailed Description by this reference, with each claim standing on itsown as a separate embodiment of the present disclosure.

What is claimed is:
 1. An apparatus comprising: an audio segmenter todivide an audio signal into a plurality of audio segments including afirst audio segment, a second audio segment temporally after andadjacent to the first audio segment, and a third audio segmenttemporally after and adjacent to the second audio segment; a binnormalizer to normalize the second audio segment to thereby create afirst normalized audio segment, the normalization based on first audiocharacteristics of the first audio segment, second audio characteristicsof the second audio segment, and third audio characteristics the thirdaudio segment; a subfingerprint generator to generate a firstsubfingerprint from the first normalized audio segment, the firstsubfingerprint including a first portion corresponding to a location ofan energy extremum in the normalized second audio segment; a portionstrength evaluator to determine a likelihood of the first portion tochange based on changes to at least one of the first audiocharacteristics, the second audio characteristics, or the third audiocharacteristics; and a portion replacer to, in response to determiningthe likelihood does not satisfy a threshold, replace the first portionwith a second portion to thereby generate a second subfingerprint. 2.The apparatus of claim 1, wherein the portion replacer is to, inresponse to determining the likelihood does not satisfy a strengththreshold, exclude the first portion when matching query subfingerprintsto the first subfingerprint.
 3. The apparatus of claim 1, furtherincluding a signal transformer to transform the audio signal into afrequency domain to thereby generate a first group of time-frequencybins corresponding to the first audio segment, a second group oftime-frequency bins corresponding to the second audio segment, and athird group of time-frequency bins corresponding to the third audiosegment; and wherein the normalizing of the second audio segmentincludes normalizing a time-frequency bin of the second group oftime-frequency bins based on a surrounding region of time-frequencybins, the surrounding region of time-frequency bins including ones ofthe first group of time-frequency bins and ones of the second group oftime-frequency bins.
 4. The apparatus of claim 1, wherein the portionstrength evaluator determines the likelihood based on changes to atleast one of the first audio characteristics, the second audiocharacteristics or the third audio characteristics by: replacing thefirst audio segment with a fourth audio segment; normalizing the secondaudio segment to thereby create a second normalized audio segment basedon second audio characteristics of the fourth audio segment and thethird audio segment; generating a second subfingerprint from thenormalized second audio segment; and determining if the secondsubfingerprint includes the first portion.
 5. The apparatus of claim 4,wherein the portion strength evaluator determines the likelihood basedon changes to at least one of the first audio characteristics, thesecond audio characteristics or the third audio characteristicsincludes: replacing the third audio segment with a fifth audio segment;normalizing the second audio segment to thereby create a thirdnormalized audio segment based on third audio characteristics of thefirst audio segment and the fifth audio segment; generating a thirdsubfingerprint from the third normalized audio segment; and determiningif the second subfingerprint includes the first portion.
 6. Theapparatus of claim 5, wherein at least one of the fourth audio segmentor the fifth audio segment is randomly generated noise audio.
 7. Theapparatus of claim 4, further including a fingerprint generator to storethe first subfingerprint and the second subfingerprint to enablematching query subfingerprints to at least one of the firstsubfingerprint or the second subfingerprint to thereby identify theaudio signal.
 8. A method comprising: dividing an audio signal into aplurality of audio segments including a first audio segment, a secondaudio segment temporally after and adjacent to the first audio segment,and a third audio segment temporally after and adjacent to the secondaudio segment; normalizing the second audio segment to thereby create afirst normalized audio segment, the normalization based on first audiocharacteristics of the first audio segment, second audio characteristicsof the second audio segment, and third audio characteristics the thirdaudio segment; generating a first subfingerprint from the firstnormalized audio segment, the first subfingerprint including a firstportion corresponding to a location of an energy extremum in thenormalized second audio segment; determining a likelihood of the firstportion to change based on changes to at least one of the first audiocharacteristics, the second audio characteristics, or the third audiocharacteristics; and in response to determining the likelihood does notsatisfy a threshold, replacing the first portion with a second portionto thereby generate a second subfingerprint.
 9. The method of claim 8,further including, in response to determining the likelihood does notsatisfy a strength threshold, excluding the first portion when matchingquery subfingerprints to the first subfingerprint.
 10. The method ofclaim 8, further including: transforming the audio signal into afrequency domain to thereby generate a first group of time-frequencybins corresponding to the first audio segment, a second group oftime-frequency bins corresponding to the second audio segment, and athird group of time-frequency bins corresponding to the third audiosegment; and wherein the normalizing the second audio segment includesnormalizing a time-frequency bin of the second group of time-frequencybins based on a surrounding region of time-frequency bins, thesurrounding region of time-frequency bins including ones of the firstgroup of time-frequency bins and ones of the second group oftime-frequency bins.
 11. The method of claim 8, wherein thedetermination of the likelihood based on changes to at least one of thefirst audio characteristics, the second audio characteristics or thethird audio characteristics includes: replacing the first audio segmentwith a fourth audio segment; normalizing the second audio segment tothereby create a second normalized audio segment based on second audiocharacteristics of the fourth audio segment and the third audio segment;generating a second subfingerprint from the normalized second audiosegment; and determining if the second subfingerprint includes the firstportion.
 12. The method of claim 11, wherein the determination of thelikelihood based on changes to at least one of the first audiocharacteristics, the second audio characteristics or the third audiocharacteristics includes: replacing the third audio segment with a fifthaudio segment; normalizing the second audio segment to thereby create athird normalized audio segment based on third audio characteristics ofthe first audio segment and the fifth audio segment; generating a thirdsubfingerprint from the third normalized audio segment; and determiningif the second subfingerprint includes the first portion.
 13. The methodof claim 11, further including storing the first subfingerprint and thesecond subfingerprint to enable matching query subfingerprints to atleast one of the first subfingerprint or the second subfingerprint tothereby identify the audio signal.
 14. A non-transitory computerreadable medium comprising instructions which, when executed, cause aprocessor to: divide an audio signal into a plurality of audio segmentsincluding a first audio segment, a second audio segment temporally afterand adjacent to the first audio segment, and a third audio segmenttemporally after and adjacent to the second audio segment; normalize thesecond audio segment to thereby create a first normalized audio segment,the normalization based on first audio characteristics of the firstaudio segment, second audio characteristics of the second audio segment,and third audio characteristics the third audio segment; generate afirst subfingerprint from the first normalized audio segment, the firstsubfingerprint including a first portion corresponding to a location ofan energy extremum in the normalized second audio segment; determine alikelihood of the first portion to change based on changes to at leastone of the first audio characteristics, the second audiocharacteristics, or the third audio characteristics; and in response todetermining the likelihood does not satisfy a threshold, replace thefirst portion with a second portion to thereby generate a secondsubfingerprint.
 15. The non-transitory computer readable medium of claim14, wherein the instructions further cause the processor to, in responseto determining the likelihood does not satisfy a strength threshold,excluding the first portion when matching query subfingerprints to thefirst subfingerprint.
 16. The non-transitory computer readable medium ofclaim 14, wherein the instructions further cause the processor to:transform the audio signal into a frequency domain to thereby generate afirst group of time-frequency bins corresponding to the first audiosegment, a second group of time-frequency bins corresponding to thesecond audio segment, and a third group of time-frequency binscorresponding to the third audio segment; and wherein the normalizingthe second audio segment includes normalizing a time-frequency bin ofthe second group of time-frequency bins based on a surrounding region oftime-frequency bins, the surrounding region of time-frequency binsincluding ones of the first group of time-frequency bins and ones of thesecond group of time-frequency bins.
 17. The non-transitory computerreadable medium of claim 14, wherein the determination of the likelihoodbased on changes to at least one of the first audio characteristics, thesecond audio characteristics or the third audio characteristicsincludes: replacing the first audio segment with a fourth audio segment;normalizing the second audio segment to thereby create a secondnormalized audio segment based on second audio characteristics of thefourth audio segment and the third audio segment; generating a secondsubfingerprint from the normalized second audio segment; and determiningif the second subfingerprint includes the first portion.
 18. Thenon-transitory computer readable medium of claim 17, wherein thedetermination of the likelihood based on changes to at least one of thefirst audio characteristics, the second audio characteristics or thethird audio characteristics includes: replacing the third audio segmentwith a fifth audio segment; normalizing the second audio segment tothereby create a third normalized audio segment based on third audiocharacteristics of the first audio segment and the fifth audio segment;generating a third subfingerprint from the third normalized audiosegment; and determining if the second subfingerprint includes the firstportion.
 19. The non-transitory computer readable medium of claim 18,wherein at least one of the fourth audio segment or the fifth audiosegment is randomly generated noise audio.
 20. The non-transitorycomputer readable medium of claim 18, wherein the instructions furthercause the processor to store the first subfingerprint and the secondsubfingerprint to enable matching query subfingerprints to at least oneof the first subfingerprint or the second subfingerprint to therebyidentify the audio signal.